<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 5.13.3

Error message:
Invalid access to memory.

Stack trace:
(000667E9) std::_Tree<std::_Tmap_traits<System::UnicodeString, void __closure
(008BCA5A) Ftpfilesystem::D2332_1
(008BEAC2) __odtbl__ TFTPFileSystem::ConfirmOverwrite
(008BB87C) Ftpfilesystem::D2332_1
(00081D3F) ntdll.dll
(0006F8BA) ntdll.dll.KiUserExceptionDispatcher

The problem happens rarely. I cannot reproduce it.