<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 5.21.6

Error message:
Out of memory

Трассировка стека:
(004400EC) System::DynArraySetLength
(004400EC) System::DynArraySetLength
(0044021D) System::DynArraySetLength

(00FDFDB9) C5412_0
(00FE1393) _ReThrowException
(00DD214A) TRetryOperationLoop::DoError
(00DD2295) TRetryOperationLoop::Error
(00DE499F) TTerminal::DoCustomCommandOnFile
(00DE46FD) TTerminal::CustomCommandOnFile
(00DE32BF) TTerminal::ProcessFiles
(00DE4B80) TTerminal::CustomCommandOnFiles
(0000BE31) TCustomScpExplorerForm::RemoteCustomCommand
(000100A8) TCustomScpExplorerForm::CustomCommand
(000119A8) TCustomScpExplorerForm::ExecuteFileOperation
(00011B41) TCustomScpExplorerForm::ExecuteFileOperation
(00011CFF) TCustomScpExplorerForm::ExecuteFileOperationCommand
(0004EDE4) TNonVisualDataModule::CustomCommandClick
(003C9C14) System::Classes::_18201
(00031331) USER32.dll
(000220E1) USER32.dll
(000209A0) USER32.dll
(000204EB) USER32.dll.DispatchMessageW

(00FDFDB9) C5412_0
(00FE1393) _ReThrowException
(00DE34D1) TTerminal::ProcessFiles
(00DE4B80) TTerminal::CustomCommandOnFiles
(0000BE31) TCustomScpExplorerForm::RemoteCustomCommand
(000100A8) TCustomScpExplorerForm::CustomCommand
(000119A8) TCustomScpExplorerForm::ExecuteFileOperation
(00011B41) TCustomScpExplorerForm::ExecuteFileOperation
(00011CFF) TCustomScpExplorerForm::ExecuteFileOperationCommand
(0004EDE4) TNonVisualDataModule::CustomCommandClick
(003C9C14) System::Classes::_18201
(00031331) USER32.dll
(000220E1) USER32.dll
(000209A0) USER32.dll
(000204EB) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.