I found out how to prevent the problem as it were, and for me, it had much to do with human error. For one, the HTTP Connect Method proxy was not, in fact, host 127.0.0.1 and TCP port 8123, but some other non-localhost on the local network and one not even running anything on TCP port 8123, and more importantly having a fake (NXDOMAIN) FQDN (a bit like, say, "shell.example.lol" [without the quotes]) that wouldn't be resolved anyway directly through WinSCP. Additionally, this particular host and TCP port 22 is the one I was intending to connect to through a HTTP Connect Method proxy at host 127.0.0.1 and TCP port 8123, a particularly-configured server daemon that would return a suitable Internet address for the fake FQDN.
For me, this problem is solved, and I'm intending to help by providing further information. Oddly the connection failure and error message occurred even though there was no infinitely-recursive proxy loop mistake involved as not even the initial connection was possible. However, something like that likely would've caused the WinSCP instance to freeze and lock up before causing the whole thing to crash or possibly even the whole session of the operating system.
L.
WinSCP 6.5.1
Error message:
Invalid access to memory.
Stack trace:
(00B748CD) C4406_0
(00EF4DCA)
(00EF6E42)
(00EF3BEC) __ExceptionHandler
(000B0C7F) ntdll.dll
(0007ABCA) ntdll.dll.KiUserExceptionDispatcher
(00B893FE) _ssh_sw_abort_deferred
(00B896C5) _ssh_is_bare
(00C94379) TSecureShell::Open
(00D2FC8E) TTerminal::Open
(00C48BBF) TTerminalThread::TerminalOpenEvent
(00C4393C) TSignalThread::Execute
(000DF45B) Userinterface::C20_0
(00014D47) KERNEL32.DLL.BaseThreadInitThunk
(0006BF09) ntdll.dll
(0006BE8C) ntdll.dll
(00EF5435)
(00EF6A0F)
(00C94560) TSecureShell::Open
(00D2FC8E) TTerminal::Open
(00C48BBF) TTerminalThread::TerminalOpenEvent
(00C4393C) TSignalThread::Execute
(000DF45B) Userinterface::C20_0
(00014D47) KERNEL32.DLL.BaseThreadInitThunk
(0006BF09) ntdll.dll
(0006BE8C) ntdll.dll
(00EF5435)
(00EF6A0F)
(00D2FE36) TTerminal::Open
(00C48BBF) TTerminalThread::TerminalOpenEvent
(00C4393C) TSignalThread::Execute
(000DF45B) Userinterface::C20_0
(00014D47) KERNEL32.DLL.BaseThreadInitThunk
(0006BF09) ntdll.dll
(0006BE8C) ntdll.dll
(00B748CD) C4406_0
(00EF4DCA)
(00EF6E42)
(00EF3BEC) __ExceptionHandler
(000B0C7F) ntdll.dll
(0007ABCA) ntdll.dll.KiUserExceptionDispatcher
(00B88C34) _ssh_conn_processed_data
(00B896F8) _ssh_is_bare
(00C99A74) TSecureShell::FreeBackend
(00C92B34) TSecureShell::~TSecureShell
(00D30057) TTerminal::Open
(00C48BBF) TTerminalThread::TerminalOpenEvent
(00C4393C) TSignalThread::Execute
(000DF45B) Userinterface::C20_0
(00014D47) KERNEL32.DLL.BaseThreadInitThunk
(0006BF09) ntdll.dll
(0006BE8C) ntdll.dll
(00EF5435)
(00EF6A0F)
(00D3045E) TTerminal::Open
(00C48BBF) TTerminalThread::TerminalOpenEvent
(00C4393C) TSignalThread::Execute
(000DF45B) Userinterface::C20_0
(00014D47) KERNEL32.DLL.BaseThreadInitThunk
(0006BF09) ntdll.dll
(0006BE8C) ntdll.dll
I know how to reproduce the problem or the problem happens frequently enough. I wish to be contacted by the WinSCP team to help resolving the problem.