<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 5.15.4

Error message:
Invalid access to memory.

Stack trace:
(00417953) System::DoneExcept
(00087D7F) ntdll.dll
(00073221) ntdll.dll.KiUserExceptionDispatcher
(003A3E28) System::Classes::_18201
(00043389) USER32.dll
(00023F87) USER32.dll
(000230D9) USER32.dll
(00022EBB) USER32.dll.DispatchMessageW

(00417540) System::HandleAnyException
(00087D7F) ntdll.dll
(00073221) ntdll.dll.KiUserExceptionDispatcher
(003A3E28) System::Classes::_18201
(00043389) USER32.dll
(00023F87) USER32.dll
(000230D9) USER32.dll
(00022EBB) USER32.dll.DispatchMessageW

Status: all_insignificant

The problem happens rarely. I cannot reproduce it.