Thanks for your report.

This bug is being tracked already:
https://winscp.net/tracker/1235

<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 5.6.2

Error message:
Invalid access to memory.

Stack trace:
[017C3F4A] _ne__sock_sslsock
[019C59AA] C4727_0
[019C7A12] ____ExceptionHandler
[019C498C] __ExceptionHandler
[7757C84E] ntdll.dll
[7757C6B6] ntdll.dll.KiUserExceptionDispatcher
[017CBBDD] _ne_ssl_get_version
[01915ED3] TWebDAVFileSystem::GetTlsVersionStr
[0190D5A6] TWebDAVFileSystem::CollectUsage
[018EFD6A] TTerminal::Open
[0185BAE3] TTerminalThread::TerminalOpenEvent
[01855844] TSignalThread::Execute
[012718B7] Userinterface::C21_0
[76A1919D] KERNEL32.DLL.BaseThreadInitThunk
[77590BB9] ntdll.dll
[77590B8C] ntdll.dll

[019C6015] C4727_0
[019C75EF] _ReThrowException
[018EFE2F] TTerminal::Open
[0185BAE3] TTerminalThread::TerminalOpenEvent
[01855844] TSignalThread::Execute
[012718B7] Userinterface::C21_0
[76A1919D] KERNEL32.DLL.BaseThreadInitThunk
[77590BB9] ntdll.dll
[77590B8C] ntdll.dll