William,
If the hypothesis that Roon is detecting one or more corrupted files is indeed a good hypothesis, and that the corruption is preventing it from completing analysis, then what you experience is exactly what is to be expected, isn’t it - because you need to remove the corrupted file(s), from the equation, download a good version and let Roon analyze a file which won’t halt it in its tracks.
Especially if a potentially corrupted file is from longer ago than one week.
As for the cover art, have you tried Settings > Setup > Clear image cache? Again a server restart afterwards will help.
Do you see anything in Settings > Library > Skipped files?