<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 6.3.3

Error message:
メモリのアクセス違反

スタック トレース:
(00AD7137) _index234
(00E2235E) C6610_3
(00E243C6) ____ExceptionHandler
(00E21180) __ExceptionHandler
(000987BF) ntdll.dll
(00077E51) ntdll.dll.KiUserExceptionDispatcher
(00ADAD6A) _sk_cleanup
(00B27C0C) CoreFinalize
(0000332E) wWinMain
(00E200C1) __wstartup
(0006AE39) ntdll.dll
(0006ADBA) ntdll.dll

The problem happens rarely. I cannot reproduce it.