<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 6.5.1

Error message:
メモリのアクセス違反

スタック トレース:
(00138EEF) System::DoneExcept
(000B0F8F) ntdll.dll
(0007ACDA) ntdll.dll.KiUserExceptionDispatcher
(00204B54) System::Classes::_18364
(00038A11) USER32.dll
(00026B88) USER32.dll
(00026015) USER32.dll
(00025B7B) USER32.dll.DispatchMessageW

(00138ADC) System::HandleAnyException
(000B0F8F) ntdll.dll
(0007ACDA) ntdll.dll.KiUserExceptionDispatcher
(00204B54) System::Classes::_18364
(00038A11) USER32.dll
(00026B88) USER32.dll
(00026015) USER32.dll
(00025B7B) USER32.dll.DispatchMessageW

Status: all_insignificant

The problem happens rarely. I cannot reproduce it.