diff --git a/slsDetectorServers/ctbDetectorServer/bin/ctbDetectorServer_developer b/slsDetectorServers/ctbDetectorServer/bin/ctbDetectorServer_developer
index c3dc5277e..4941442b6 100755
Binary files a/slsDetectorServers/ctbDetectorServer/bin/ctbDetectorServer_developer and b/slsDetectorServers/ctbDetectorServer/bin/ctbDetectorServer_developer differ
diff --git a/slsDetectorServers/ctbDetectorServer/slsDetectorFunctionList.c b/slsDetectorServers/ctbDetectorServer/slsDetectorFunctionList.c
index eadf83efb..0ef6c3721 100644
--- a/slsDetectorServers/ctbDetectorServer/slsDetectorFunctionList.c
+++ b/slsDetectorServers/ctbDetectorServer/slsDetectorFunctionList.c
@@ -2158,8 +2158,9 @@ int configureMAC() {
 
     // start addr
     uint32_t addr = RXR_ENDPOINT_START_REG;
-    // get struct memory
-    udp_header *udp = (udp_header *)(Blackfin_getBaseAddress() + addr / 2);
+    // build udp header
+    udp_header header;
+    udp_header *udp = &header;
     memset(udp, 0, sizeof(udp_header));
 
     //  mac addresses
@@ -2191,6 +2192,13 @@ int configureMAC() {
 
     calcChecksum(udp);
 
+    // force FPGA writes to be aligned and in order
+    uint32_t words[sizeof(udp_header) / sizeof(uint32_t)];
+    memcpy(words, udp, sizeof(udp_header));
+    for (size_t i = 0; i != sizeof(words) / sizeof(words[0]); ++i) {
+        bus_w(addr + i * 2, words[i]);
+    }
+
     cleanFifos(); // FIXME: resetPerpheral() for ctb?
     resetPeripheral();
     LOG(logINFO, ("Waiting for %d s for mac to be up\n",
diff --git a/slsDetectorServers/gotthard2DetectorServer/bin/gotthard2DetectorServer_developer b/slsDetectorServers/gotthard2DetectorServer/bin/gotthard2DetectorServer_developer
index 00714c679..3fa7a1b35 100755
Binary files a/slsDetectorServers/gotthard2DetectorServer/bin/gotthard2DetectorServer_developer and b/slsDetectorServers/gotthard2DetectorServer/bin/gotthard2DetectorServer_developer differ
diff --git a/slsDetectorServers/gotthard2DetectorServer/slsDetectorFunctionList.c b/slsDetectorServers/gotthard2DetectorServer/slsDetectorFunctionList.c
index 39761d91f..50d148b06 100644
--- a/slsDetectorServers/gotthard2DetectorServer/slsDetectorFunctionList.c
+++ b/slsDetectorServers/gotthard2DetectorServer/slsDetectorFunctionList.c
@@ -2052,9 +2052,9 @@ void setupHeader(int iRxEntry, int vetoInterface, uint32_t destip,
         iRxEntry += RXR_ENDPOINTS_MAX;
     }
     addr += (iRxEntry * RXR_ENDPOINT_OFST);
-    // get struct memory
-    udp_header *udp =
-        (udp_header *)(Nios_getBaseAddress() + addr / (sizeof(u_int32_t)));
+    // build udp header
+    udp_header header;
+    udp_header *udp = &header;
     memset(udp, 0, sizeof(udp_header));
 
     //  mac addresses
@@ -2085,6 +2085,14 @@ void setupHeader(int iRxEntry, int vetoInterface, uint32_t destip,
     // total length is redefined in firmware
 
     calcChecksum(udp);
+
+    // force FPGA writes to be aligned and in order
+    uint32_t words[sizeof(udp_header) / sizeof(uint32_t)];
+    memcpy(words, udp, sizeof(udp_header));
+    for (size_t i = 0; i != sizeof(words) / sizeof(words[0]); ++i) {
+        bus_w(addr + i * sizeof(uint32_t), words[i]);
+    }
+
     if (iRxEntry < numUdpDestinations) {
         LOG(logINFO, ("\tIP checksum : 0x%lx\n\n", udp->ip_checksum));
     }
diff --git a/slsDetectorServers/jungfrauDetectorServer/bin/jungfrauDetectorServer_developer b/slsDetectorServers/jungfrauDetectorServer/bin/jungfrauDetectorServer_developer
index f7ce83250..a4215538a 100755
Binary files a/slsDetectorServers/jungfrauDetectorServer/bin/jungfrauDetectorServer_developer and b/slsDetectorServers/jungfrauDetectorServer/bin/jungfrauDetectorServer_developer differ
diff --git a/slsDetectorServers/jungfrauDetectorServer/slsDetectorFunctionList.c b/slsDetectorServers/jungfrauDetectorServer/slsDetectorFunctionList.c
index 72244a4eb..9b53f906f 100644
--- a/slsDetectorServers/jungfrauDetectorServer/slsDetectorFunctionList.c
+++ b/slsDetectorServers/jungfrauDetectorServer/slsDetectorFunctionList.c
@@ -1870,8 +1870,9 @@ void setupHeader(int iRxEntry, enum interfaceType type, uint32_t destip,
                                    : RXR_ENDPOINT_OUTER_START_REG);
     // calculate rxr endpoint offset
     addr += (iRxEntry * RXR_ENDPOINT_OFST);
-    // get struct memory
-    udp_header *udp = (udp_header *)(Blackfin_getBaseAddress() + addr / 2);
+    // build udp header
+    udp_header header;
+    udp_header *udp = &header;
     memset(udp, 0, sizeof(udp_header));
 
     //  mac addresses
@@ -1902,6 +1903,14 @@ void setupHeader(int iRxEntry, enum interfaceType type, uint32_t destip,
     // total length is redefined in firmware
 
     calcChecksum(udp);
+
+    // force FPGA writes to be aligned and in order
+    uint32_t words[sizeof(udp_header) / sizeof(uint32_t)];
+    memcpy(words, udp, sizeof(udp_header));
+    for (size_t i = 0; i != sizeof(words) / sizeof(words[0]); ++i) {
+        bus_w(addr + i * 2, words[i]);
+    }
+
     if (iRxEntry < numUdpDestinations) {
         LOG(logINFO, ("\tIP checksum : 0x%lx\n\n", udp->ip_checksum));
     }
diff --git a/slsDetectorServers/moenchDetectorServer/bin/moenchDetectorServer_developer b/slsDetectorServers/moenchDetectorServer/bin/moenchDetectorServer_developer
index 385d20902..46e044d6d 100755
Binary files a/slsDetectorServers/moenchDetectorServer/bin/moenchDetectorServer_developer and b/slsDetectorServers/moenchDetectorServer/bin/moenchDetectorServer_developer differ
diff --git a/slsDetectorServers/moenchDetectorServer/slsDetectorFunctionList.c b/slsDetectorServers/moenchDetectorServer/slsDetectorFunctionList.c
index b3cb6fe69..37cb91edb 100644
--- a/slsDetectorServers/moenchDetectorServer/slsDetectorFunctionList.c
+++ b/slsDetectorServers/moenchDetectorServer/slsDetectorFunctionList.c
@@ -1203,8 +1203,9 @@ void setupHeader(int iRxEntry, enum interfaceType type, uint32_t destip,
                                    : RXR_ENDPOINT_OUTER_START_REG);
     // calculate rxr endpoint offset
     addr += (iRxEntry * RXR_ENDPOINT_OFST);
-    // get struct memory
-    udp_header *udp = (udp_header *)(Blackfin_getBaseAddress() + addr / 2);
+    // build udp header
+    udp_header header;
+    udp_header *udp = &header;
     memset(udp, 0, sizeof(udp_header));
 
     //  mac addresses
@@ -1235,6 +1236,14 @@ void setupHeader(int iRxEntry, enum interfaceType type, uint32_t destip,
     // total length is redefined in firmware
 
     calcChecksum(udp);
+
+    // force FPGA writes to be aligned and in order
+    uint32_t words[sizeof(udp_header) / sizeof(uint32_t)];
+    memcpy(words, udp, sizeof(udp_header));
+    for (size_t i = 0; i != sizeof(words) / sizeof(words[0]); ++i) {
+        bus_w(addr + i * 2, words[i]);
+    }
+
     if (iRxEntry < numUdpDestinations) {
         LOG(logINFO, ("\tIP checksum : 0x%lx\n\n", udp->ip_checksum));
     }
diff --git a/slsDetectorServers/mythen3DetectorServer/bin/mythen3DetectorServer_developer b/slsDetectorServers/mythen3DetectorServer/bin/mythen3DetectorServer_developer
index 42517d6f5..d6530e548 100755
Binary files a/slsDetectorServers/mythen3DetectorServer/bin/mythen3DetectorServer_developer and b/slsDetectorServers/mythen3DetectorServer/bin/mythen3DetectorServer_developer differ
diff --git a/slsDetectorServers/mythen3DetectorServer/slsDetectorFunctionList.c b/slsDetectorServers/mythen3DetectorServer/slsDetectorFunctionList.c
index 8c7f107aa..8d9bc4881 100644
--- a/slsDetectorServers/mythen3DetectorServer/slsDetectorFunctionList.c
+++ b/slsDetectorServers/mythen3DetectorServer/slsDetectorFunctionList.c
@@ -2225,9 +2225,9 @@ int configureMAC() {
         uint32_t addr = BASE_UDP_RAM;
         // calculate rxr endpoint offset
         addr += (iRxEntry * RXR_ENDPOINT_OFST); // TODO: is there round robin
-        // get struct memory
-        udp_header *udp =
-            (udp_header *)(Nios_getBaseAddress() + addr / (sizeof(u_int32_t)));
+        // build udp header
+        udp_header header;
+        udp_header *udp = &header;
         memset(udp, 0, sizeof(udp_header));
 
         //  mac addresses
@@ -2258,6 +2258,14 @@ int configureMAC() {
         // total length is redefined in firmware
 
         calcChecksum(udp);
+
+        // force FPGA writes to be aligned and in order
+        uint32_t words[sizeof(udp_header) / sizeof(uint32_t)];
+        memcpy(words, udp, sizeof(udp_header));
+        for (size_t i = 0; i != sizeof(words) / sizeof(words[0]); ++i) {
+            bus_w(addr + i * sizeof(uint32_t), words[i]);
+        }
+
         if (iRxEntry < numUdpDestinations) {
             LOG(logINFO, ("\tIP checksum : 0x%lx\n\n", udp->ip_checksum));
         }
diff --git a/slsDetectorServers/slsDetectorServer/include/arm64.h b/slsDetectorServers/slsDetectorServer/include/arm64.h
index eb79100d8..3cf3e5aae 100644
--- a/slsDetectorServers/slsDetectorServer/include/arm64.h
+++ b/slsDetectorServers/slsDetectorServer/include/arm64.h
@@ -6,8 +6,10 @@
 #include <sys/types.h>
 
 void bus_w(u_int32_t offset, u_int32_t data);
+void bus_w_csp1(u_int32_t offset, u_int32_t data);
 void bus_w_csp2(u_int32_t offset, u_int32_t data);
 u_int32_t bus_r(u_int32_t offset);
+u_int32_t bus_r_csp1(u_int32_t offset);
 u_int32_t bus_r_csp2(u_int32_t offset);
 uint64_t getU64BitReg(int aLSB, int aMSB);
 void setU64BitReg(uint64_t value, int aLSB, int aMSB);
diff --git a/slsDetectorServers/slsDetectorServer/src/arm64.c b/slsDetectorServers/slsDetectorServer/src/arm64.c
index 034a9856b..14ffa3385 100644
--- a/slsDetectorServers/slsDetectorServer/src/arm64.c
+++ b/slsDetectorServers/slsDetectorServer/src/arm64.c
@@ -28,6 +28,18 @@ void bus_w(u_int32_t offset, u_int32_t data) {
     *ptr1 = data;
 }
 
+void bus_w_csp1(u_int32_t offset, u_int32_t data) {
+    volatile u_int32_t *ptr1;
+    ptr1 = (u_int32_t *)(csp1base + offset / (sizeof(u_int32_t)));
+    *ptr1 = data;
+}
+
+u_int32_t bus_r_csp1(u_int32_t offset) {
+    volatile u_int32_t *ptr1;
+    ptr1 = (u_int32_t *)(csp1base + offset / (sizeof(u_int32_t)));
+    return *ptr1;
+}
+
 u_int32_t bus_r(u_int32_t offset) {
     volatile u_int32_t *ptr1;
     ptr1 = (u_int32_t *)(csp0base + offset / (sizeof(u_int32_t)));
diff --git a/slsDetectorServers/xilinx_ctbDetectorServer/bin/xilinx_ctbDetectorServer_developer b/slsDetectorServers/xilinx_ctbDetectorServer/bin/xilinx_ctbDetectorServer_developer
index c9b913eb0..fac5a1915 100755
Binary files a/slsDetectorServers/xilinx_ctbDetectorServer/bin/xilinx_ctbDetectorServer_developer and b/slsDetectorServers/xilinx_ctbDetectorServer/bin/xilinx_ctbDetectorServer_developer differ
diff --git a/slsDetectorServers/xilinx_ctbDetectorServer/slsDetectorFunctionList.c b/slsDetectorServers/xilinx_ctbDetectorServer/slsDetectorFunctionList.c
index 04d95fc0b..cffde6ef5 100644
--- a/slsDetectorServers/xilinx_ctbDetectorServer/slsDetectorFunctionList.c
+++ b/slsDetectorServers/xilinx_ctbDetectorServer/slsDetectorFunctionList.c
@@ -1502,8 +1502,9 @@ int configureMAC() {
     }
 #endif
 
-    // get struct memory
-    udp_header *udp = (udp_header *)(Arm_getUDPBaseAddress());
+    // build udp header
+    udp_header header;
+    udp_header *udp = &header;
     memset(udp, 0, sizeof(udp_header));
 
     //  mac addresses
@@ -1535,6 +1536,13 @@ int configureMAC() {
 
     calcChecksum(udp);
 
+    // force FPGA writes to be aligned and in order
+    uint32_t words[sizeof(udp_header) / sizeof(uint32_t)];
+    memcpy(words, udp, sizeof(udp_header));
+    for (size_t i = 0; i != sizeof(words) / sizeof(words[0]); ++i) {
+        bus_w_csp1(i * sizeof(uint32_t), words[i]);
+    }
+
     return OK;
 }
 
diff --git a/slsSupportLib/include/sls/versionAPI.h b/slsSupportLib/include/sls/versionAPI.h
index 76e7ea009..6e7cda8ec 100644
--- a/slsSupportLib/include/sls/versionAPI.h
+++ b/slsSupportLib/include/sls/versionAPI.h
@@ -3,11 +3,11 @@
 /** API versions */
 #define APILIB        "0.0.0 0x250909"
 #define APIRECEIVER   "0.0.0 0x250822"
-#define APICTB        "0.0.0 0x261028"
-#define APIGOTTHARD2  "0.0.0 0x261028"
-#define APIMOENCH     "0.0.0 0x261028"
+#define APICTB        "0.0.0 0x261103"
+#define APIGOTTHARD2  "0.0.0 0x261103"
+#define APIMOENCH     "0.0.0 0x261103"
 #define APIEIGER      "0.0.0 0x261027"
-#define APIXILINXCTB  "0.0.0 0x261028"
-#define APIJUNGFRAU   "0.0.0 0x261028"
-#define APIMYTHEN3    "0.0.0 0x261028"
+#define APIXILINXCTB  "0.0.0 0x261103"
+#define APIJUNGFRAU   "0.0.0 0x261103"
+#define APIMYTHEN3    "0.0.0 0x261103"
 #define APIMATTERHORN "0.0.0 0x260529"