Is this a bug maybe?

I’ve noticed lately that Roon occasionally fails to show cover art as shown below…

This is the case for all instances of the picture involved; the thumbnail and the now playing screens. If I check the file data and tags, everything is there but Roon refuses to show it. It’s only one or two pictures, seemingly randomly dropped from Roon and the only way to get them back is to restart the core. I have the “prefer file” option selected in the Import Settings page.
Any ideas?