<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 6.3.2

Error message:
Invalid access to memory.

Stack trace:
(00AB1C8F)
(0003F54E) ntdll.dll.ZwWow64CallFunction64
(0003FCCA) ntdll.dll.KiUserExceptionDispatcher
(00AB5B59)
(00AB6004)
(00ABB6A7)
(00AB63D9)
(00AC4DD6)
(00AC0B34)
(00BC5C1F)
(00BC7DB5)
(00BA2AD7)
(000C19D3)
(002757F0)
(00359731)
(00226F88)
(00007E6F) USER32.DLL.CallNextHookEx
(000080CC) USER32.DLL
(0000966A) USER32.DLL
(000096DB) USER32.DLL.DispatchMessageW

Status: unknown_rel_addr

The problem happens rarely. I cannot reproduce it.