Index: cloudsync/handlers/cs_mft_dcs_request_handler.py
===================================================================
diff -u -r3ecfe17da0e7fb115cc97ed14014d9c13aa87a8f -rf6c1d0be3c250785357d92318fa0662656f0f61d
--- cloudsync/handlers/cs_mft_dcs_request_handler.py	(.../cs_mft_dcs_request_handler.py)	(revision 3ecfe17da0e7fb115cc97ed14014d9c13aa87a8f)
+++ cloudsync/handlers/cs_mft_dcs_request_handler.py	(.../cs_mft_dcs_request_handler.py)	(revision f6c1d0be3c250785357d92318fa0662656f0f61d)
@@ -425,6 +425,14 @@
                     # Step #3 - upload the device log file in chunks
                     # Duplicate detection relies on 409 at start-session (immediate, no wasted chunks).
 
+                    if not os.path.exists(device_log_data['path']):
+                        self.logger.warning(f"Device log file no longer available: {device_log_data['path']}")
+                        error = Error.general(OutboundMessageIDs.CS2UI_ERROR.value,
+                                              ErrorIDs.CS_DEVICE_LOG_ERROR.value,
+                                              f"Device log file no longer available: {device_log_data['path']}")
+                        self.error_handler.enqueue_error(error=error)
+                        return
+
                     device_log_json = helpers_construct_device_log_json(device_log_data)
 
                     upload_result = cmd_outgoing_upload_file_in_chunks(base_url=base_url,
@@ -516,6 +524,10 @@
 
                     # Step #3 - upload the cs log file
 
+                    if not os.path.exists(cs_log_data['path']):
+                        self.logger.warning(f"CS log file no longer available: {cs_log_data['path']}")
+                        return
+
                     cs_log_json = helpers_construct_cs_log_json(cs_log_data)
 
                     cs_log_filename = cmd_outgoing_upload_file_in_chunks(base_url=base_url,
@@ -532,8 +544,18 @@
 
                     if isinstance(cs_log_filename, dict) and not cs_log_filename.get("accepted"):
                         self.logger.info(f"CS log file rejected as duplicate: {cs_log_filename.get('filename')}")
+                        try:
+                            os.remove(cs_log_data['path'])
+                            self.logger.info(f"Duplicate CS log file cleaned up: {cs_log_data['path']}")
+                        except OSError:
+                            pass  # already removed by log retention
                     elif isinstance(cs_log_filename, str):
                         self.logger.debug(f"CS log file uploaded: {cs_log_filename}")
+                        try:
+                            os.remove(cs_log_data['path'])
+                            self.logger.info(f"Uploaded CS log file cleaned up: {cs_log_data['path']}")
+                        except OSError:
+                            pass
 
                 else:
                     error = Error.general(OutboundMessageIDs.CS2UI_ERROR.value,
Index: cloudsync/handlers/logs_handler.py
===================================================================
diff -u -ra923c3f28c864ca51557deeabebcaa576147ae4c -rf6c1d0be3c250785357d92318fa0662656f0f61d
--- cloudsync/handlers/logs_handler.py	(.../logs_handler.py)	(revision a923c3f28c864ca51557deeabebcaa576147ae4c)
+++ cloudsync/handlers/logs_handler.py	(.../logs_handler.py)	(revision f6c1d0be3c250785357d92318fa0662656f0f61d)
@@ -3,14 +3,17 @@
 from cloudsync.utils.globals import *
 
 from logging.handlers import TimedRotatingFileHandler
-from time import time
+from time import time, sleep
+from threading import Thread
 
 class CustomTimedRotatingFileHandlerHandler(TimedRotatingFileHandler):
     """
     Handler for logging to a file, rotating the log file and uploading it to cloud at certain timed intervals.
     It extends the official TimedRotatingFileHandler to add the upload functionality.
     """
 
+    _upload_in_progress = False
+
     def __init__(self, filename, prelogger: Logger, *args, **kwargs):
         super().__init__(filename, *args, **kwargs)
         self.network_request_handler = None
@@ -34,7 +37,13 @@
     def __select_files_to_upload(cls):
         """
         Checks for existing rotated files in the directory (excluding the newly created one) and uploads them.
+        Spawns a background thread to upload files sequentially, waiting for each to complete
+        before starting the next. This prevents queue saturation when multiple backlogged
+        files exist (e.g. after extended offline periods).
         """
+        if cls._upload_in_progress:
+            return  # previous batch still draining
+
         # We use the cls.baseFilename because according to code documentation:
         # the filename passed in, could be a path object (see Issue #27493),
         # but cls.baseFilename will be a string
@@ -46,9 +55,29 @@
                 existing_files.append(os.path.join(os.path.dirname(cls.baseFilename), filename))
 
         if len(existing_files) > 0:
-            for existing_file in existing_files:
-                cls.__upload_cs_log_file(existing_file)
+            existing_files.sort(key=lambda x: os.path.getmtime(x))  # oldest first
+            cls._upload_in_progress = True
+            Thread(target=cls.__upload_files_sequentially,
+                   args=(existing_files,), daemon=True).start()
 
+    def __upload_files_sequentially(cls, files):
+        """
+        Uploads CS log files one at a time, waiting for the network queue to drain
+        between each upload. This ensures all backlogged files are uploaded without
+        saturating the single-slot network queue.
+        """
+        try:
+            for f in files:
+                if not os.path.exists(f):
+                    continue  # deleted by log retention or previous upload
+                cls.__upload_cs_log_file(f)
+                # Wait for network queue to drain before next file
+                while len(cls.network_request_handler.queue) > 0:
+                    sleep(1)
+                sleep(2)  # yield to bus-initiated requests
+        finally:
+            cls._upload_in_progress = False
+
     def __upload_cs_log_file(cls, log_file_path):
 
         cs_log_data = {