It is not.
Thanks StFeder. Much appreciated.
"Works for me" is a stupid reply, for what should be an obvious reason.
The answer confirms the problem isn't universal, and points you to a couple of areas which could be causing, or have caused the problem?
Those of us who help here on the forums often deal with all sorts of questions, for people with all levels of technical capability. Often the first conclusion they jump to is "Bug". Often they don't actually provide much, if any information, and expect others on the forum to be mind readers.
So, we throw out a bit of information, perhaps ask a question, and see if we can get enough information to actually help.
Brian has given a further hint. Perhaps if you told us what version you upgraded from and to, and when, and what you did as part of the upgrade. Perhaps if you read my whole answer and realised that I mentioned there was a problem with settings for one version of MC21, which is why I asked you to check settings. Perhaps if you explained whether you use a Cover Art folder, or put your Cover Art next to the media file. Perhaps if you explained why you would have Cover Art files hidden. Then perhaps we may be able to help.