<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 5.19.6

Error message:
Invalid access to memory.

Stack trace:
(000B051F) TTerminalManager::DisconnectActiveTerminalIfPermanentFreeOtherwise
(0008788F) ntdll.dll
(00073EC1) ntdll.dll.KiUserExceptionDispatcher
(000223D0) TCustomScpExplorerForm::ShowExtendedException
(000B1FBD) TTerminalManager::TerminalShowExtendedException
(00DC7C3C) TTerminal::ShowExtendedException
(0024432A) Vcl::Forms::TApplication::HandleException
(003C7B64) System::Classes::_18201
(00040099) USER32.dll
(00037055) USER32.dll
(00036732) USER32.dll
(000348D6) USER32.dll.CallWindowProcW
(00079E57) COMCTL32.DLL
(00079EF6) COMCTL32.DLL
(00079CAC) COMCTL32.DLL
(00040099) USER32.dll
(00037055) USER32.dll
(00036732) USER32.dll
(000348D6) USER32.dll.CallWindowProcW
(0049E76B) Dragdrop::TDragDrop::WndMethod
(003C7B64) System::Classes::_18201
(00040099) USER32.dll
(00037055) USER32.dll
(00034DC5) USER32.dll
(00034B8B) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.