This bug has been added to the tracker:
https://winscp.net/tracker/1235

Thanks for your report.
I have sent you an email with a debug version of WinSCP to address you have used to register on this forum.

Trying to connect to an instance of eXist-database behind httpd-reverseproxy via WebDAV, I get the error -see below.
It is possible to connect this way in Oxygen (XML-Editor), so basically the setup seems to be working.
I was also able to connect to a local instance of eXist via WebDAV.

best,
matej


-------------
WinSCP 5.6.2

Error message:
Invalid access to memory.

Stack trace:
[01603F4A] _ne__sock_sslsock
[018059AA] C4727_0
[01807A12] ____ExceptionHandler
[0180498C] __ExceptionHandler
[7718C84E] ntdll.dll
[7718C6B6] ntdll.dll.KiUserExceptionDispatcher
[0160BBDD] _ne_ssl_get_version
[01755ED3] TWebDAVFileSystem::GetTlsVersionStr
[0174D5A6] TWebDAVFileSystem::CollectUsage
[0172FD6A] TTerminal::Open
[0169BAE3] TTerminalThread::TerminalOpenEvent
[01695844] TSignalThread::Execute
[010B18B7] Userinterface::C21_0
[74DD919D] KERNEL32.DLL.BaseThreadInitThunk
[771A0BB9] ntdll.dll
[771A0B8C] ntdll.dll

[01806015] C4727_0
[018075EF] _ReThrowException
[0172FE2F] TTerminal::Open
[0169BAE3] TTerminalThread::TerminalOpenEvent
[01695844] TSignalThread::Execute
[010B18B7] Userinterface::C21_0
[74DD919D] KERNEL32.DLL.BaseThreadInitThunk
[771A0BB9] ntdll.dll
[771A0B8C] ntdll.dll