Artist art (again!)

So, I see there have been a number of posts on this topic before, and a number of fixes suggested in some instances, none of which have helped in my case.

My problem is that for two of the artists in my music collection artist photos don’t appear, Moloko and The Chicks (new name for what were The Dixie Chicks). I’ve checked and double checked the ID3 tags for misspellings, weird characters, trailing / leading spaces, you name it, but they’re both OK.

I’ve looked up both artists on and both are present and have artist photos present.

I can’t see anything weird or unusual about either names, like possible conflicts with other similar sounding names, so any ideas what could be wrong here?