I'm having trouble getting a Smartlist to recognize audio tracks that don't have artwork. I have a modified version of the stock "Audio - Missing Cover Art" smartlist; I added a couple of fields to exclude some tracks that I know don't have (and will never have) artwork. But lately - in the last month or two - I've been noticing tracks that don't have any artwork, aren't explicitly excluded from the Smartlist, but are still not displayed in the Smartlist.
The attached screenshots show an example. The first one, "let it rhyme.jpg", shows a track with no artwork. There is no thumbnail in the list view (yes I tried rebuilding the thumbnail, to no avail) and the tag display in the Action Window shows no image.
The second screenshot shows the smartlist in question, "Test empty cover art". The shot shows both the rules and the contents of the list, and it doesn't contain the "Let It Rhyme" track. The rules for the smartlist are
Media Type is Audio
Comment does not contain "__NO_ARTWORK__"
Image File is <empty>
Artist is not any <short list of excluded artists>
The track in question definitely does not contain a "__NO_ARTWORK__" comment, and its artist is not in the excluded group.
There are dozens of tracks in my library which have this problem. Sometimes it's all of the tracks on one album with no artwork. Sometimes it's on an album with just one track (which has no artwork). Sometimes it's an album with one track missing artwork and, and the rest of the tracks on the album have artwork. In all of these cases, the smartlist no longer catches the "missing artwork" tracks.
Any ideas as to what might be going wrong?
iMac, macOS 10.15, MC 25.0.108