<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 5.17.10

Error message:
Invalid access to memory.

Stack trace:
(00CBF1E4)
(00094F6F) ntdll.dll
(00075CD1) ntdll.dll.KiUserExceptionDispatcher
(00019504)
(000195AE)
(0027AD15)
(0027A35C)
(003A5978)
(00031301) USER32.dll
(000225A7) USER32.dll
(00021F42) USER32.dll.CallWindowProcW
(0047CCAF)
(003A5978)
(00031301) USER32.dll
(000225A7) USER32.dll
(00020EB0) USER32.dll
(00020A0B) USER32.dll.DispatchMessageW

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.