Thanks for your response.
As a postscript, I found a restart of MB got the rotation going again. So I queued an obscure Aussie artist again and replicated the problem. I waited for a change in artist, this time Dr.John, and a right click selecting "next picture" brought a picture for few seconds before displaying the album artist colours again. I restarted MB again and Dr. John pictures rotated automatically without a problem.
Maybe I need to avoid obscure Aussie artists

Do you think then that the problem is my internet connection?