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 5.13.3

Error message:
External exception C0000029

Stack trace:
(0008F2B6) ntdll.dll
(00045C86) ntdll.dll.RtlRaiseStatus
(00045B12) ntdll.dll.KiUserExceptionDispatcher
(008BC9EA) ___doGlobalUnwind
(008BEBD6) ____ExceptionHandler
(008BB87C) __ExceptionHandler
(00045C86) ntdll.dll.RtlRaiseStatus
(00045B12) ntdll.dll.KiUserExceptionDispatcher
(004D6188) Jclhookexcept::_16408
(008BD0C5) C5104_0
(008BE5F8) _ThrowExceptionLDTC
(0071A2A5) TSCPFileSystem::CopyToRemote
(007CE9B9) TTerminal::CopyToRemote
(0000E73E) TCustomScpExplorerForm::ExecuteFileOperation
(00020564) TCustomScpExplorerForm::RemoteFileControlDragDropFileOperation
(000206F0) TCustomScpExplorerForm::RemoteFileControlDDFileOperation
(0067994E) TUnixDirView::PerformItemDragDropOperation
(0041FA86) Customdirview::TCustomDirView::DDProcessDropped
(0044331F) Dragdrop::TDragDrop::WndMethod
(00380370) System::Classes::_18201
(0001B4B4) USER32.dll
(0001B5B2) USER32.dll
(0001BBE4) USER32.dll
(0001BC3B) USER32.dll.DispatchMessageW

(0008F2B6) ntdll.dll
(00045C86) ntdll.dll.RtlRaiseStatus
(00045B12) ntdll.dll.KiUserExceptionDispatcher
(008BC9EA) ___doGlobalUnwind
(008BEBD6) ____ExceptionHandler
(008BB87C) __ExceptionHandler
(00045C86) ntdll.dll.RtlRaiseStatus
(00045B12) ntdll.dll.KiUserExceptionDispatcher
(004D6188) Jclhookexcept::_16408
(008BD0C5) C5104_0
(008BE5F8) _ThrowExceptionLDTC
(007BB5B1) TTerminal::CommandError
(007BD948) TTerminal::ReadDirectory
(007BB261) TTerminal::DoEndTransaction
(007BB162) TTerminal::EndTransaction%

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.