Zugriffsverletzung - ung�ltiger Zugriff auf den Speicher - _sshfwd_unthrottle

<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 5.7.6

Error message:
Zugriffsverletzung - ung�ltiger Zugriff auf den Speicher.

Stack trace:
(003ADE1B) System::SysFreeMem
(0005A7EA) ntdll.dll
(0000F15E) ntdll.dll.KiUserExceptionDispatcher
(007D25AF) ___org_free
(005E1557) _safefree
(005E4AEF) C2232_0
(005F3591) _sshfwd_unthrottle
(006A8318) TSecureShell::FreeBackend
(006A15B8) TSecureShell::~TSecureShell
(006D475D) TSFTPFileSystem::~TSFTPFileSystem
(0070B13F) TTerminal::~TTerminal
(00075346) TManagedTerminal::~TManagedTerminal
(0007668C) TTerminalManager::FreeTerminal
(00075CEF) TTerminalManager::FreeActiveTerminal
(0001AB28) TCustomScpExplorerForm::ShowExtendedException
(00077BDD) TTerminalManager::TerminalShowExtendedException
(0070F0E8) TTerminal::ShowExtendedException
(003402A8) System::Classes::_18201
(000152F7) USER32.dll
(00015D35) USER32.dll
(000167CE) USER32.dll
(00016895) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.