diff --git a/csaxs_bec/bec_ipython_client/plugins/OMNY_shared/tomo_queue_mixin.py b/csaxs_bec/bec_ipython_client/plugins/OMNY_shared/tomo_queue_mixin.py
index f91f71a..e3b7cb1 100644
--- a/csaxs_bec/bec_ipython_client/plugins/OMNY_shared/tomo_queue_mixin.py
+++ b/csaxs_bec/bec_ipython_client/plugins/OMNY_shared/tomo_queue_mixin.py
@@ -421,6 +421,20 @@ class TomoQueueMixin:
         """
 
         def _run():
+            # tomo_id_manager.FALLBACK_TOMO_ID (0) means add_sample_database()
+            # never actually registered anything server-side (no valid
+            # e-account) -- there's no real "new.pdf" slot reserved for this
+            # session, so uploading would just claim whatever number
+            # countersaver.txt currently happens to hold, i.e. some unrelated
+            # real measurement's slot. Skip rather than risk clobbering it.
+            if self.tomo_id == self.tomo_id_manager.FALLBACK_TOMO_ID:
+                print(
+                    f"Skipping PDF upload: tomo_id={self.tomo_id} means no real "
+                    "measurement was registered (not a valid e-account) -- "
+                    "there's no samples-folder slot to upload into."
+                )
+                return
+
             try:
                 import base64
 
@@ -451,13 +465,13 @@ class TomoQueueMixin:
                         allow_redirects=False,  # SSRF hardening
                     )
                     if r.status_code != 200:
-                        print(f"PDF upload to {url} -> HTTP {r.status_code}: {r.text[:120]}")
+                        print(f"PDF upload to {url} -> HTTP {r.status_code}: {r.text[:400]}")
                         continue
                     if expected_name not in r.text:
                         print(
                             f"PDF upload to {url} succeeded but the server-assigned "
                             f"filename doesn't match tomo_id {self.tomo_id} (response: "
-                            f"{r.text[:120]!r}) -- a concurrent measurement "
+                            f"{r.text[:400]!r}) -- a concurrent measurement "
                             "registration may have raced this upload."
                         )
                     else: