There were two instances of WinSCP running. Both were in a similar state of having lost the connection during 'Keep Remote Up To Date'. Only one instance of WinSCP crashed.

WinSCP was set to 'Keep Remote Up To Date'.
Remote machine shutdown suddenly.
WinSCP timed out (became aware the connection was lost).
After a minute or so, I clicked in the WinSCP dialog that had popped up, I clicked something like "OK" to acknowledge to WinSCP had lost the connection. Then it popped with a crash.

WinSCP 5.13.5

Error message:
Invalid access to memory.

Stack trace:
(003F2A9F) System::DoneExcept
(00083FFF) ntdll.dll
(00071931) ntdll.dll.KiUserExceptionDispatcher
(00380EE0) System::Classes::_18201
(00045359) USER32.dll
(00036297) USER32.dll
(000353D6) USER32.dll
(000351AB) USER32.dll.DispatchMessageW

(003F268C) System::HandleAnyException
(00083FFF) ntdll.dll
(00071931) ntdll.dll.KiUserExceptionDispatcher
(00380EE0) System::Classes::_18201
(00045359) USER32.dll
(00036297) USER32.dll
(000353D6) USER32.dll
(000351AB) USER32.dll.DispatchMessageW

Status: all_insignificant

The problem happens rarely. I cannot reproduce it.