Invalid access to memory - std::_Tree<std::_Tmap_traits<System::UnicodeString, void __closure

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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.