<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)>

WinSCP 5.7.7

Error message:
Invalid%20access%20to%20memory.%0D%0A%0D%0AStack%20trace%3A%0D%0A%28001D686F%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3AIsFormSizeStored%0D%0A%2800062496%29%20ntdll.dll

Status: not_matched

The problem happens rarely. I cannot reproduce it.