<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 6.3.7

Error message:
Nieprawidłowy dostęp do pamięci.

Stack trace:
(004C4DF1) Dragdropfilesex::_16407
(000B0C7F) ntdll.dll
(0007ABCA) ntdll.dll.KiUserExceptionDispatcher
(004C6029) Dragdropfilesex::TDropTargetFilesEx::RenderDropped
(004C3B72) Dragdrop::TDragDrop::GetFromClipboard
(00AE9EC8) TUnixDirView::PasteFromClipBoard
(000292A3) TCustomScpExplorerForm::PasteFromClipBoard
(000612C5) TScpCommanderForm::PasteFromClipBoard
(0004FFE7) TNonVisualDataModule::ExplorerActionsExecute
(0027581C) System::Actions::TContainedActionList::ExecuteAction
(003595FD) Vcl::Actnlist::TCustomAction::Execute
(004E965A) Tb2item::TTBPopupMenu::IsShortCut

The problem happens rarely. I cannot reproduce it.