Let me roughly explain my plan: If I had a concrete reproducer for this problem it would be easy to determine the cause and deal with the circumstances, e.g. checking the retry handling if a file is occupied, prevent overwrites from file-system monitoring (if there are any) … but here I have no starting clue. Whan I can do is to review the code and strategically consider logging or alerting on any possile error condition. Alerting might not be wanted in terms of UX (prevent interruptions), and manuals (it needs translations), so I might build a special version with debugging features. All of that needs some planning and focus.
Btw. which platform and OS are you on?