Artwork display inconsistent?

Hi, I just got a RPi 3 and installed volumio, very happy with it so far! Just one thing bugs me: artwork isn’t always displayed correctly for my tracks.

Now I’ve searched online and found various explanations, but they all seemed to boil down to difficulties with displaying the correct artwork when browsing the library. I don’t worry about this, what happens in my case is that artwork isn’t always displayed correctly on the playback screen. Furthermore I can’t even seem to be able to find any commonality between the tracks that have their album art displayed and those that don’t. For example, I have “Alchemy” and “Brothers in Arms” by Dire Straits in my library. In both cases, the files are ALAC m4a files ripped from the original CDs with iTunes and the album art is embedded as a png file (945x945) for “Brothers in Arms”, 953x953 for “Alchemy”. When I play a “Brothers in Arms” track, the artworks shows up fine, and the album cover shows up when I browse the list of albums. When I play an “Alchemy” track on the other hand, only the generic black “volumio” artwork is displayed, same in the album list.

Does anybody have an idea of what’s happening here? (Or is 950x950 some magic artwork size limit? If that’s the case, can it be changed? I’m happy to manually edit a source / config file if it comes to that.)