<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 6.1.1

Error message:
メモリのアクセス違反

スタック トレース:
(00DA35C7) TSessionData::SetProxyDNS
(0100350E) C6083_0
(01005576) ____ExceptionHandler
(01002330) __ExceptionHandler
(0009783F) ntdll.dll
(000777B1) ntdll.dll.KiUserExceptionDispatcher
(00D1C547) TTerminalQueue::GetIsEmpty
(0000A0C7) TCustomScpExplorerForm::AddQueueItem
(00017855) TCustomScpExplorerForm::ExecutedFileChanged
(000804C9) TEditorManager::CheckFileChange
(0007E192) TEditorManager::FileChanged
(00E4B137) TEditorForm::SaveFile
(00E4B1B4) TEditorForm::EditorActionsExecute
(003467AD) Vcl::Actnlist::TCustomAction::Execute
(003B4BC1) Vcl::Forms::TCustomForm::CloseQuery
(003F62DD) Vcl::Controls::TWinControl::WndProc
(003B07EC) Vcl::Forms::TCustomForm::WndProc

(01003B79) C6083_0
(01005153) _ReThrowException
(00080509) TEditorManager::CheckFileChange
(0007E192) TEditorManager::FileChanged
(00E4B137) TEditorForm::SaveFile
(00E4B1B4) TEditorForm::EditorActionsExecute
(003467AD) Vcl::Actnlist::TCustomAction::Execute
(003B4BC1) Vcl::Forms::TCustomForm::CloseQuery
(003F62DD) Vcl::Controls::TWinControl::WndProc
(003B07EC) Vcl::Forms::TCustomForm::WndProc

The problem happens rarely. I cannot reproduce it.