Invalid access to memory - _ssh_agent_forwarding_permitted

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WinSCP 5.9

Error message:
Invalid access to memory.

Stack trace:
(0061B6AC) C2447_0
(0086216E) C5073_3
(008641D6) ____ExceptionHandler
(00860F90) __ExceptionHandler
(0008147F) ntdll.dll
(0006F02A) ntdll.dll.KiUserExceptionDispatcher
(00622530) _ssh_agent_forwarding_permitted
(00627E6B) _sshfwd_x11_is_local
(006281F3) _sshfwd_x11_is_local
(0061B5CE) C2447_0
(0061B781) C2447_0
(0061BA9C) _ssh_connshare_log
(0064A4A5) _select_result
(006FAEB7) TSecureShell::HandleNetworkEvents
(006FB17A) TSecureShell::ProcessNetworkEvents
(006FA76B) TSecureShell::WaitForData
(006F5B75) TSecureShell::Init
(006F544A) TSecureShell::Open
(0073352B) TSFTPFileSystem::Open
(0076DE53) TTerminal::Reopen
(006C57B9) TTerminalThread::TerminalReopenEvent
(006C0780) TSignalThread::Execute
(0009836F) Userinterface::C20_0
(000152C2) KERNEL32.DLL.BaseThreadInitThunk
(0005F717) ntdll.dll
(0005F6DF) ntdll.dll

(008627D9) C5073_3
(00863DB3) _ReThrowException
(006F5C83) TSecureShell::Init
(006F544A) TSecureShell::Open
(0073352B) TSFTPFileSystem::Open
(0076DE53) TTerminal::Reopen
(006C57B9) TTerminalThread::TerminalReopenEvent
(006C0780) TSignalThread::Execute
(0009836F) Userinterface::C20_0
(000152C2) KERNEL32.DLL.BaseThreadInitThunk
(0005F717) ntdll.dll
(0005F6DF) ntdll.dll
Authentication failed.

The problem happens rarely. I cannot reproduce it.