Why does iTunes incorrectly replace my album artwork without my permission?
I keep trying to change artwork, only to find that iTunes has replaced my input artwork with (1) the previous artwork, or (2) artwork for an entirely unrelated album in my collection, or (3) some different artwork from iTunes Store (e.g. a compilation album featuring the track). I have done everything I can to stop iTunes replacing artwork, but it keeps happening. A typical situation is that I paste in the artwork then it gets replaced a few hours later by artwork from a random album in my collection.
One particular example: I downloaded a label sampler compilation, but I wanted to list the tracks according to the albums they were sourced from, so I could have the year, album name and artwork to give more context to the track. That took some effort on my part and iTunes seems to react badly to this, often reverting or randomly changing the artwork I added, as described above.
One possible issue: I have just over 25,000 tracks, which is above iTunes Match's capability (and that's annoying in itself), so I'm wondering if there's a synchronisation problem, but even so replacing artwork seems a rather random event.
Any help much appreciated before I give up on iTunes and find something that I can control.
Thanks
MacBook Pro (Retina, 13-inch, Late 2013), OS X El Capitan (10.11.1), iTunes Match subscription
