I think this might be because some files are missing from both the NAS and the Windows 11 machine. In this case the application needs to re-check whether those are available from the NAS in case they have appeared there in the meantime. You could check this by typing “missing” in the search bar and selecting the STATUS missing entry.
Incidentally, I’ve just observed a related behavior with one of my test libraries, where the download activity very briefly pops up once every second. I’ll look into that – the fix for that might also affect how the application behaves in your case.