iTunes Library Weirdness - Random HLS Media Encoding (MOVPKG

I have a couple of Apple devices including an iMac, iPad & Mac Mini. I use Apple Music and the Cloud Library sync to ensure my music is available on all my devices (I have a ton of music stored in iTunes going back to the early 2000's, some bought from the iTunes Store but lots copied from CD's). All my CD's are burned to my Mac mini and then are sync'd across to my other devices.

Recently I noticed that the iTunes library on my iMac was looking very strange. Many albums were totally missing from the library or only a handful of tracks showing. But on the Mac Mini, all looks perfectly fine. In the file system on the iMac, the Music>Media>Music folder aligns to what I can see in iTunes, but the Music>Media>Apple Music folder contains hundreds of 'missing' albums and tracks. Bizarrely, many albums purchased as CD's and copied onto the Mac Mini originally are split in half on the iMac. Finder says these 'missing' files are HLS Media and the majority have a MOVPKG extension - which I think is an Apple TV format.

Looking for patterns, I don't see anything obvious. Older and newer albums are affected. Purchased and music owned outright similarly. Albums I've had for years and never touched, are now split in 2, and half the tracks encoded as MOVPKG. It's as if iTunes on my iMac is slowly combing through the entire library and randomly selecting albums to wreck. I have raised a support track with Apple, but after a few encouraging calls, they ghosted me and I've heard nothing from them in weeks. As stated earlier, my library on a Mac Mini seems good.

Interested in any similar experiences, and hoping that someone has an idea how to 'correct' the HLS Media encoding. Many thanks in advance.