<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 6.3.3

Error message:
Acesso inválido à memória

Rastreamento de pilha:
(00288E52) System::Sysutils::ByteType
(00E2235E) C6610_3
(00E243C6) ____ExceptionHandler
(00E21180) __ExceptionHandler
(00098CCF) ntdll.dll
(000781E1) ntdll.dll.KiUserExceptionDispatcher
(00B7EA93) UnixIncludeTrailingBackslash
(00B88A2A) TRemoteFileList::GetFullDirectory
(00B884A8) TRemoteFile::GetFullFileName
(00B848D9) TRemoteFile::Duplicate
(00B8883A) TRemoteFileList::CloneStrings
(00011FB9) TCustomScpExplorerForm::ExecuteCopyMoveFileOperation
(00012B5C) TCustomScpExplorerForm::ExecuteFileOperation
(00012DD8) TCustomScpExplorerForm::ExecuteFileOperation
(00012F97) TCustomScpExplorerForm::ExecuteFileOperationCommand
(0001311E) TCustomScpExplorerForm::ExecuteCopyOperationCommand
(0004FBA1) TNonVisualDataModule::ExplorerActionsExecute
(00275A24) System::Actions::TContainedActionList::ExecuteAction
(00359965) Vcl::Actnlist::TCustomAction::Execute
(002271BC) System::Classes::_18201
(000324C1) USER32.dll
(00023311) USER32.dll
(00021BB0) USER32.dll
(000216FB) USER32.dll.DispatchMessageW

(00E229C9) C6610_3
(00E23FA3) _ReThrowException
(00B84936) TRemoteFile::Duplicate
(00B8883A) TRemoteFileList::CloneStrings
(00011FB9) TCustomScpExplorerForm::ExecuteCopyMoveFileOperation
(00012B5C) TCustomScpExplorerForm::ExecuteFileOperation
(00012DD8) TCustomScpExplorerForm::ExecuteFileOperation
(00012F97) TCustomScpExplorerForm::ExecuteFileOperationCommand
(0001311E) TCustomScpExplorerForm::ExecuteCopyOperationCommand
(0004FBA1) TNonVisualDataModule::ExplorerActionsExecute
(00275A24) System::Actions::TContainedActionList::ExecuteAction
(00359965) Vcl::Actnlist::TCustomAction::Execute
(002271BC) System::Classes::_18201
(000324C1) USER32.dll
(00023311) USER32.dll
(00021BB0) USER32.dll
(000216FB) USER32.dll.DispatchMessageW

The problem happens rarely. I cannot reproduce it.