Thanks for your feedback.
Issue not reproduced on latest release v5.9 (6786)
<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
<If relevant, consider attaching a session log file or a screenshot)>
uploading big file of size 439 MB (in background)
WinSCP 5.7.7
Error message:
Error occurred during logging. It's been turned off.
Out of memory
Status: not_matched
I know how to reproduce the problem or the problem happens frequently enough. I wish to be contacted by the WinSCP team to help resolving the problem.