diff --git a/services/capture/deltacast-bridge/main.c b/services/capture/deltacast-bridge/main.c
index d38e3e2..97e6363 100644
--- a/services/capture/deltacast-bridge/main.c
+++ b/services/capture/deltacast-bridge/main.c
@@ -36,7 +36,9 @@ static ULONG rx_streamtype(unsigned port) {
         case 1: return VHD_ST_RX1;
         case 2: return VHD_ST_RX2;
         case 3: return VHD_ST_RX3;
-        default: return VHD_ST_RX0;
+        default:
+            fprintf(stderr, "{\"error\":\"port %u not supported (max 3)\"}\n", port);
+            return VHD_ST_RX0; /* caller will fail on signal lock */
     }
 }
 
@@ -294,6 +296,7 @@ int main(int argc, char *argv[]) {
             }
             VHD_UnlockSlotHandle(slot);
         } else if (r != VHDERR_TIMEOUT) {
+            fprintf(stderr, "[video] VHD_LockSlotHandle error %lu — stopping\n", r);
             break;
         }
     }