<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 6.3.5

Error message:
Accès mémoire invalide.

Trace de la pile :
(002A3BEB) System::SysFreeMem
(00E24572) C6612_0
(00E265DA) ____ExceptionHandler
(00E23394) __ExceptionHandler
(00098E4F) ntdll.dll
(000781B1) ntdll.dll.KiUserExceptionDispatcher
(00E1216F) ___org_free
(00AD6667) _safefree
(00AD492D) C3930_0
(00AD49F8) C3930_0
(00AD4A3B) _conf_new
(00AD4A60) _conf_free
(00BC4E06) TSecureShell::Open
(00C600C8) TTerminal::OpenTunnel
(00C5E337) TTerminal::Open
(00B7EB03) TTerminalThread::TerminalOpenEvent
(00B79934) TSignalThread::Execute
(000D246B) Userinterface::C20_0
(00016BA7) KERNEL32.DLL.BaseThreadInitThunk
(0006B0C9) ntdll.dll
(0006B04A) ntdll.dll

(00E24BDD) C6612_0
(00E261B7) _ReThrowException
(00BC4FB0) TSecureShell::Open
(00C600C8) TTerminal::OpenTunnel
(00C5E337) TTerminal::Open
(00B7EB03) TTerminalThre

The problem happens rarely. I cannot reproduce it.

<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 5.17.10

Error message:
Invalid access to memory.

Stack trace:
(00BCFC30) C2605_0
(00F8A13A) C5296_0
(00F8C1A2) ____ExceptionHandler
(00F88F5C) __ExceptionHandler
(0006248E) ntdll.dll
(0000F15E) ntdll.dll.KiUserExceptionDispatcher
(00BCFD4C) C2605_0
(00BCFDA3) _conf_new
(00BCFDC8) _conf_free
(00BD7496) _log_free
(00D01B7F) TSecureShell::ResetConnection
(00D018A0) TSecureShell::~TSecureShell
(00D52B80) TSFTPFileSystem::~TSFTPFileSystem
(00D89ADF) TTerminal::~TTerminal
(000AADAA) TManagedTerminal::~TManagedTerminal
(000AC569) TTerminalManager::FreeTerminal
(000AC37A) TTerminalManager::FreeAll
(000AB37F) TTerminalManager::~TTerminalManager
(000AAE50) TTerminalManager::DestroyInstance
(0010390E) Execute
(00002658) wWinMain
(00F8814D) __wstartup
(00038800) ntdll.dll
(000387D0) ntdll.dll

The problem happens rarely. I cannot reproduce it.