<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 6.5.4

Error message:
メモリのアクセス違反

スタック トレース:
(00139BC4) System::UStrAsg
(000B345F) ntdll.dll
(0007A7CA) ntdll.dll.KiUserExceptionDispatcher

Status: all_insignificant

The problem happens rarely. I cannot reproduce it.