Copying files to remote side failed - ___cleanupTObject

<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 5.7.5

Error message:
Copying files to remote side failed.

Invalid access to memory.

Stack trace:
(007E3995) ___cleanupTObject
(007E39EA) C4799_0
(007E5A52) ____ExceptionHandler
(007E29CC) __ExceptionHandler
(0003F04E) ntdll.dll.ZwWow64CallFunction64
(0003F7CA) ntdll.dll.KiUserExceptionDispatcher
(007E5743) _CatchCleanup
(006F812C) TSFTPFileSystem::SFTPSourceRobust
(006F724A) TSFTPFileSystem::CopyToRemote
(00722639) TTerminal::CopyToRemote
(0067349B) TUploadQueueItem::DoExecute
(00670C77) TTerminalItem::ProcessEvent
(0066F128) TSignalThread::Execute
(00082687) Userinterface::C21_0
(00016C02) KERNEL32.DLL.BaseThreadInitThunk
(00059D5D) ntdll.dll
(00059D25) ntdll.dll

(007E3995) ___cleanupTObject
(007E39EA) C4799_0
(007E5A52) ____ExceptionHandler
(007E29CC) __ExceptionHandler
(0003F04E) ntdll.dll.ZwWow64CallFunction64
(0003F7CA) ntdll.dll.KiUserExceptionDispatcher
(007E5743) _CatchCleanup
(006F812C) TSFTPFileSystem::SFTPSourceRobust
(006F724A) TSFTPFileSystem::CopyToRemote
(00722639) TTerminal::CopyToRemote
(0067349B) TUploadQueueItem::DoExecute
(00670C77) TTerminalItem::ProcessEvent
(0066F128) TSignalThread::Execute
(00082687) Userinterface::C21_0
(00016C02) KERNEL32.DLL.BaseThreadInitThunk
(00059D5D) ntdll.dll
(00059D25) ntdll.dll

The problem happens rarely. I cannot reproduce it.

<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 5.9.3

Error message:
Copying files to remote side failed.

Invalid access to memory.

Stack trace:
(008663CD) ___cleanupTObject
(00866422) C5073_3
(0086848A) ____ExceptionHandler
(00865244) __ExceptionHandler
(00081D3F) ntdll.dll
(0006F8EA) ntdll.dll.KiUserExceptionDispatcher
(008672BB) C5073_3
(008682D1) ____ExceptionHandler
(00865244) __ExceptionHandler
(00081D3F) ntdll.dll
(008663B2) ___doGlobalUnwind
(0086859E) ____ExceptionHandler
(00865244) __ExceptionHandler
(00081D3F) ntdll.dll
(0006F8EA) ntdll.dll.KiUserExceptionDispatcher
(004B9160) Jclhookexcept::_16408
(003E52C2) System::NewUnicodeString
(003E52C2) System::NewUnicodeString
(004B4585) Jcldebug::TJclStackInfoList::AddToStrings
(000C4B8A) Wininterface::C23_0
(000C4EEA) Wininterface::C23_0
(004B8EAD) Jclhookexcept::_16404
(004B9070) Jclhookexcept::_16407
(004B918D) Jclhookexcept::_16409
(00854022) C3337_0
(00866422) C5073_3
(0086848A) ____ExceptionHandler
(00865244) __ExceptionHandler
(00081D3F) ntdll.dll
(0006F8EA) ntdll.dll.KiUserExceptionDispatcher
(0075B585) TSFTPFileSystem::SFTPSourceRobust
(0075A6BA) TSFTPFileSystem::CopyToRemote
(007872D5) TTerminal::CopyToRemote
(0000DCB0) TCustomScpExplorerForm::ExecuteFileOperation
(0001F6BC) TCustomScpExplorerForm::RemoteFileControlDragDropFileOperation
(0001F848) TCustomScpExplorerForm::RemoteFileControlDDFileOperation
(0065578E) TUnixDirView::PerformItemDragDropOperation
(0040847A) Customdirview::TCustomDirView::DDProcessDropped
(0042CA1F) Dragdrop:%3

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.

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.