This bug has been added to the tracker:
https://winscp.net/tracker/1697

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.

<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 5.14.1

Error message:
Invalid access to memory.

Stack trace:
(006AC4C4) TBookmarkList::FindByName
(0008341F) ntdll.dll
(000711F1) ntdll.dll.KiUserExceptionDispatcher
(0002A195) TCustomScpExplorerForm::CreateOpenDirMenu
(00050913) TScpCommanderForm::CopyFilesToClipboard
(004A62DA) Tbx::TTBXItemViewer::CalcSize
(0048F17C) Tb2item::TTBView::NotifyFocusEvent
(00492866) Tb2item::TTBModalHandler::Loop
(004919F7) Tb2item::_16725
(0049F4A2) Tb2toolbar::TTBCustomToolbar::~TTBCustomToolbar
(00269DE0) Vcl::Controls::TControl::CheckNewSize
(00269E2F) Vcl::Controls::TControl::WMRButtonDblClk
(0026E2E1) Vcl::Controls::_17076
(0026D928) Vcl::Controls::TWinControl::ControlAtPos
(00397BBC) System::Classes::_18208
(00045269) USER32.dll
(000361B7) USER32.dll
(000352E6) USER32.dll
(000350BB) USER32.dll.DispatchMessageW

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.