Invalid access to memory - Customdirview::TCustomDirView::KeyDown

<Try to describe precise steps that lead to the problem (where do you click, what keys do you press, what do you see, etc.)>
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WinSCP 5.21.7

Error message:
Invalid access to memory.

Stack trace:
(0046A5D0) Customdirview::TCustomDirView::KeyDown
(00087B7F) ntdll.dll
(00074001) ntdll.dll.KiUserExceptionDispatcher

The problem happens rarely. I cannot reproduce it.