<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 6.7

Error message:
Accès mémoire invalide.

Trace de la pile :
(0016CF56) System::UStrAsg
(000B51E0) ntdll.dll
(000B51AF) ntdll.dll
(0006CC4E) ntdll.dll
(0007962A) ntdll.dll
(00023FD9) USER32.dll
(00169700) System::FreeMem
(0016CB5C) System::UStrClr
(003C8A26) Vcl::Controls::TControl::GetTextBuf
(0039CF22) System::Internal::Strhlpr::UnicodeAssign
(001621DE) System::UnicodeString::operator =
(00ACD0CC) TTerminal::FileModified
(00955C68) TFileOperationProgressType::SetFile
(009559A3) TFileOperationProgressType::GetCancel
(00AD504B) TTerminal::ChangeFileProperties
(009558C9) TFileOperationProgressType::Finish
(009559A3) TFileOperationProgressType::GetCancel
(00AD167B) TTerminal::ProcessFiles
(001B3D56) System::Generics::Collections::TListHelper::DoRemoveFwd4
(0016B8F6) System::TMonitor::Exit
(00226CBE) System::Classes::RemoveFixups
(003C762D) Vcl::Controls::TControl::~TControl
(0021DE9F) System::Classes::TPersistent::~TPersistent
(003CC409) Vcl::Controls::TWinControl::~TWinControl
(0016CB5C) System::UStrClr
(0016B640) System::TMonitor::Destroy
(0016AE45) System::TObject::CleanupInstance
(00BAB00A) TPropertiesDialog::~TPropertiesDialog
(0039CF31) System::Internal::Strhlpr::UnicodeFree
(00AD57CE) TTerminal::ChangeFilesProperties
(0039CF31) System::Internal::Strhlpr::UnicodeFree
(00AD57A7) TTerminal::ChangeFilesProperties
(0039CF22) System::Internal::Strhlpr::UnicodeAssign
(001621DE) System::UnicodeString::operator =
(0002091E) TCustomScpExplorerForm::SetProperties
(0002781B) USER32.dll
(00040403) USER32.dll
(00221671) System::Classes::TStringList::InsertItem
(0002015B) TCustomScpExplorerForm::ExecuteFileOperation
(0052132F) Nortonlikelistview::TCustomNortonLikeListView::GetNextItem
(005349E5) Customdirview::TCustomDirView::CustomCreateFileList
(00021856) TCustomScpExplorerForm::ExecuteFileOperation
(00040403) USER32.dll
(0039CF31) System::Internal::Strhlpr::UnicodeFree
(00021BEA) TCustomScpExplorerForm::ExecuteFileOperationCommand
(00045163) TCustomScpExplorerForm::IsBusy
(00062E4E) TNonVisualDataModule::GetBusy
(009AE1AD) TRemoteFile::GetIsParentDirectory
(00045185) TCustomScpExplorerForm::AllowedAction
(00058821) TNonVisualDataModule::ExplorerActionsExecute
(008ED91A) TUnixDirView::ItemIsFile
(00447B1C) Vcl::Comctrls::TCustomListView::GetFocused
(00534EE8) Customdirview::TCustomDirView::AnyFileSelected
(000528DC) TNonVisualDataModule::ExplorerActionsUpdate
(000382E7) ntdll.dll
(00251F6C) System::Actions::TContainedActionList::ExecuteAction
(0016B13A) System::CallDynaInst
(0051E6E3) Listviewcolproperties::TCustomListViewColProperties::SetVisibleInternal
(003B6A79) Vcl::Actnlist::TCustomAction::Execute
(002343AF) System::Classes::TBasicActionLink::Execute
(00576A48) Tb2item::TTBCustomItem::Click
(0057693B) Tb2item::TTBCustomItem::ClickWndProc
(00235394) System::Classes::_18364
(00038CC1) USER32.dll
(00027D78) USER32.dll
(00027A6

The problem happens rarely. I cannot reproduce it.