So it sometimes disappears for a few tracks but it will come back in later tracks.
You haven’t been using NAA input long enough but over time you will see/hear
Going backwards in a playlist is not a common way to listen (sometimes I do it).
But the fact that static comes (in the first place) when going to next track is more of a problem.
So it sounds like you are experience exactly what I reported months ago really.
UP NAA input is not 100% reliable anymore. BUt it actually was at one point !
That’s exactly what I reported - 'like bad FM reception radio"
This was reported in November last year: