I have recently noticed a problem with the artist image feature. This only seems to happen on a small number of images - say one out of every 30 or so - which is still a lot when you have a lot of music.
What happens is that I add a new artist image, which fills the screen due to the dimensions. It seems to work, but when I navigate away from it and come back, the artist image is replaced with black. Roon still seems to think that the artist image is there, as I can click on it and the black “pops up” like a normal image would. If I go to the artist editor, it is still showing the image as it should look.