Cannot%20focus%20a%20disabled%20or%20invisible%20window%0D%0A%0D%0AStack%20trace%3A%0D%0A%28001DBBED%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3ASetFocus

<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:
Cannot%20focus%20a%20disabled%20or%20invisible%20window%0D%0A%0D%0AStack%20trace%3A%0D%0A%28001DBBED%29%20Vcl%3A%3AForms%3A%3ATCustomForm%3A%3ASetFocus

Status: not_matched

The problem happens rarely. I cannot reproduce it.