Thanks for your report.
I have sent you an email with a debug version of WinSCP to the address you have used to register on this forum.
<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 5.13.8
Error message:
External exception C0000006
Stack trace:
(007EC14C) TCopyDialog::TCopyDialog
(0007E19F) ntdll.dll
(0006BD81) ntdll.dll.KiUserExceptionDispatcher
(00007540) TCustomScpExplorerForm::CopyParamDialog
(00042BF8) TScpCommanderForm::CopyParamDialog
(0000E639) TCustomScpExplorerForm::ExecuteFileOperation
(0002064C) TCustomScpExplorerForm::RemoteFileControlDragDropFileOperation
(000207D8) TCustomScpExplorerForm::RemoteFileControlDDFileOperation
(0067C00E) TUnixDirView::PerformItemDragDropOperation
(00420832) Customdirview::TCustomDirView::DDProcessDropped
(00444103) Dragdrop::TDragDrop::WndMethod
(0038109C) System::Classes::_18201
(0003AF19) USER32.dll
(000373E5) USER32.dll
(00036C99) USER32.dll
(00036A7B) USER32.dll.DispatchMessageW
I know how to reproduce the problem or the problem happens frequently enough. I wish to be contacted by the WinSCP team to help resolving the problem.