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 5.7.7

Error message:
Invalid access to memory.

Stack trace:
(0003F03B) TScpCommanderForm::LocalDirViewDDTargetHasDropHandler
(000689FA)ntdll.dll
(00068E5E)ntdll.dll
(0006B2C9)ntdll.dll
(0006B547)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.