You can mark the attachment as private (it's mentioned in my very first post above).
Before posting, please read how to report bug or request support effectively.
Bug reports without an attached log file are usually useless.
I also have been having the same error message while transferring thousands of files. Seems like the same issue
Approx 10-15 minutes.
No, it happens even when I have one connection open.
The strange things is when I shut down the client via Taskmanager and restart it, it works... for the time being.