Apple Music splits albums up on iPhone 15

I notice that people have had this problem for over a year, particularly on iOS 17. I have just updated to iOS 18 and have a similar problem. I should say that I am NOT signed up to Apple Music because it has messed up my Family Music library in the past - substituting the wrong album covers, and even changing albums when it doesn't recognise old ones that are no longer for sale eg: 1970s/80s compilation albums. About a third of my music I have digitised from vinyl record or compact cassette, another third is ripped from CDs, and the final third is digital downloads from the iTunes Store and Amazon Music (about half and half).

What surprises me is that my iPhone (presumably after the iOS date recently) has split up some compilation albums into a few fragments with different tracks in different albums, seemingly at random (10 track in one block, then 3 in another, then 2 with only one track each) - and these are albums that were only ever available in vinyl!

At this juncture, I should point out that the problem doesn't occur in MacOS, in neither Ventura Apple Music (desktop) nor Mojave iTunes (desktop). It happens seemingly spontaneously on the iPhone, sometime AFTER (sometimes weeks after) being downloaded from my iMac via USB lead.

A less than satisfactory solution I have found is to delete all the artists from each track, and say they were all sung by some mysterious artist called 'Various'. Then load the album into the phone (after deleting the original copy).

Is apple going to fix this? What is causing it? There should be flag to say: "This is complete album leave it alone!". And before you point out , Yes, I have ticked the box "This Album is a compilation of songs by various artist", and it does sweet f-all.