<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 5.21.5

Error message:
Invalid access to memory.

Stack trace:
(0043CEF8) System::HandleAnyException
(00097F5F) ntdll.dll
(00076171) ntdll.dll.KiUserExceptionDispatcher
(003C9C0C) System::Classes::_18201
(00046D70) USER32.dll
(00026125) USER32.dll
(00024A53) USER32.dll
(0002458B) USER32.dll.DispatchMessageW

Status: all_insignificant

The problem happens rarely. I cannot reproduce it.