diff --git a/image_pusher/TCPStreamPusher.cpp b/image_pusher/TCPStreamPusher.cpp
index f4c9b5ac..371ac472 100644
--- a/image_pusher/TCPStreamPusher.cpp
+++ b/image_pusher/TCPStreamPusher.cpp
@@ -377,7 +377,12 @@ bool TCPStreamPusher::ReadExactPersistent(Connection& c, void* buf, size_t len)
 }
 
 void TCPStreamPusher::WriterThread(Connection* c) {
-    while (c->active) {
+    // Drain the queue until the end sentinel. We deliberately do NOT stop on c->active
+    // alone: StopDataCollectionThreads() clears active and then pushes the sentinel, and
+    // every DATA frame enqueued before that sentinel must still be sent. Otherwise END
+    // (sent by EndDataCollection after stopping this thread) could overtake images that
+    // are merely waiting in the queue, and the writer would finalize before receiving them.
+    while (true) {
         auto e = c->queue.GetBlocking();
         if (e.end)
             break;
@@ -944,6 +949,14 @@ bool TCPStreamPusher::EndDataCollection(const EndMessage& message) {
 
     for (auto& cptr : local_connections) {
         auto& c = *cptr;
+
+        // Flush all queued DATA before sending END: stopping the writer thread drains the
+        // send queue and joins it, so every image is on the wire before END goes out. This
+        // prevents END from overtaking images still waiting in the queue when the writer
+        // thread has fallen behind (e.g. on a loaded machine), which would make the remote
+        // writer finalize early and silently drop the trailing images.
+        StopDataCollectionThreads(c);
+
         if (c.broken) {
             ret = false;
             continue;
@@ -962,9 +975,6 @@ bool TCPStreamPusher::EndDataCollection(const EndMessage& message) {
             ret = false;
     }
 
-    for (auto& c : local_connections)
-        StopDataCollectionThreads(*c);
-
     {
         std::lock_guard lg(connections_mutex);
         session_connections.clear();