@gonghuiii: 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 5.19.6

Error message:
External exception C000001D

Stack trace:
(0003F030) std::_Tree<std::_Tmap_traits<System::UnicodeString, TParallelOperation::TDirectoryData, std::less<System::UnicodeString>, std::allocator<std::pair<const System::UnicodeString, TParallelOperation::TDirectoryData> >, 0> >::erase
(00051D8E)ntdll.dll
(00052091)ntdll.dll

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.