<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 6.5.6

Error message:
Invalid access to memory.

Stack trace:
(6552440B)WinSCP.exe
(000B353F) ntdll.dll
(0007A7AA) ntdll.dll.KiUserExceptionDispatcher
(00D3927A) TTerminal::EndTransaction
(00D70D52) DoConsoleDialog
(00024842) TCustomScpExplorerForm::OpenConsole
(000614B1) TScpCommanderForm::OpenConsole
(000551F2) TNonVisualDataModule::ExplorerActionsExecute
(00221868) System::Actions::TContainedActionList::ExecuteAction
(0038AA71) Vcl::Actnlist::TCustomAction::Execute
(00204C90) System::Classes::_18364
(000383B1) USER32.dll
(00027178) USER32.dll
(00026145) USER32.dll
(00025CAB) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.