<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 5.17.7

Error message:
External exception EEFFACE

Stack trace:
(00000370)mswsock.dll
(00F8862A) C5296_3
(00F8A692) ____ExceptionHandler
(00F8744C) __ExceptionHandler
(0006246E) ntdll.dll
(0000F12E) ntdll.dll.KiUserExceptionDispatcher
(000021FC) WS2_32.DLL.WSAEnumNetworkEvents
(00D07082) TSecureShell::EnumNetworkEvents
(00D077D9) TSecureShell::ProcessNetworkEvents
(00D06DBB) TSecureShell::WaitForData
(00D0435A) TSecureShell::Receive
(00D5543C) TSFTPFileSystem::ReceivePacket
(00D567C4) TSFTPFileSystem::ReceiveResponse
(00D80BA3) TSFTPQueue::ReceiveResponse
(00D6CDEC) TSFTPQueue::ReceivePacket
(00D7DFC0) TSFTPFileSystem::Sink
(00DA9DF5) TTerminal::Sink
(00DA8DCE) TTerminal::SinkRobust
(00DA8C14) TTerminal::DoCopyToLocal
(00D7B57A) TSFTPFileSystem::CopyToLocal
(00DA875F) TTerminal::CopyToLocal
(0000FD70) TCustomScpExplorerForm::ExecuteCopyMoveFileOperation
(00010848) TCustomScpExplorerForm::ExecuteFileOperation
(00010A39) TCustomScpExplorerForm::ExecuteFileOperation
(00010ABF) TCustomScpExplorerForm::ExecuteFileOperationCommand
(00010C46) TCustomScpExplorerForm::ExecuteCopyOperationCommand
(000440FF) TNonVisualDataModule::ExplorerActionsExecute
(003E85CC) System::Actions::TContainedActionList::ExecuteAction
(001C71B5) Vcl::Actnlist::TCustomAction::Execute
(003A4BA8) System::Classes::_18201
(00015307) USER32.dll
(00015D45) USER32.dll
(000167D2) USER32.dll
(00016895) USER32.dll.DispatchMessageW

(0000B5AF) KERNELBASE.dll.RaiseException
(0006246E) ntdll.dll
(0000F12E)

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 5.15.9

Error message:
Kopírování souborů do vzdáleného adresáře selhalo.

Chyba přístupu do paměti.

Stack trace:
(00000370)mswsock.dll
(0092812A) C5157_3
(0092A192) ____ExceptionHandler
(00926F4C) __ExceptionHandler
(0006246E) ntdll.dll
(0000F12E) ntdll.dll.KiUserExceptionDispatcher
(000021FC) WS2_32.DLL.WSAEnumNetworkEvents
(00795756) TSecureShell::EnumNetworkEvents
(00795E8D) TSecureShell::ProcessNetworkEvents
(00793A73) TSecureShell::Send
(007DD77D) TSFTPFileSystem::SendPacket
(0080C876) TSFTPUploadQueue::SendPacket
(008028BC) TSFTPFileSystem::Source
(00832313) TTerminal::Source
(00830F3E) TTerminal::SourceRobust
(00830D7D) TTerminal::DoCopyToRemote
(007FF552) TSFTPFileSystem::CopyToRemote
(0082FACD) TTerminal::CopyToParallel
(0082FC3D) TTerminal::CopyParallel
(008307A0) TTerminal::CopyToRemote
(0074ED15) TUploadQueueItem::DoTransferExecute
(0074D936) TQueueItem::Execute
(0074C96A) TTerminalItem::ProcessEvent
(0074AD00) TSignalThread::Execute
(000BB6A3) Userinterface::C20_0
(0001243B) kernel32.dll.BaseThreadInitThunk
(00038810) ntdll.dll
(000387E0) ntdll.dll

(00928795) C5157_3
(00929D6F) _ReThrowException
(00830F7B) TTerminal::SourceRobust
(00830D7D) TTerminal::DoCopyToRemote
(007FF552) TSFTPFileSystem::CopyToRemote
(0082FACD) TTerminal::CopyToParallel
(0082FC3D) TTerminal::CopyParallel
(008307A0) TTerminal::CopyToRemote
(0074ED15) TUploadQueueItem::DoTransferExecute
(0074D936) TQue

The problem happens rarely. I cannot reproduce it.