<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 5.11.1

Error message:
Invalid access to memory.

Stack trace:
(0007565E) TFrameAnimation::Repaint
(000851DF) ntdll.dll
(00073161) ntdll.dll.KiUserExceptionDispatcher
(007E7C0B) TFileFindDialog::StartStopButtonClick
(00257BA1) Vcl::Controls::TWinControl::WndProc
(001BFD30) Vcl::Stdctrls::TButtonControl::WndProc
(00257D07) Vcl::Controls::_17076
(00257BA1) Vcl::Controls::TWinControl::WndProc
(00212068) Vcl::Forms::TCustomForm::WndProc

The problem happens rarely. I cannot reproduce it.