Tony, been reading your posts. Had nothing to add as I don't know what is going on. Not sure why there is an issue. I can only narrow it down to sync (which can be turned on and off) that is the cause.
I quickly copy my iTunes library to an SSD drive anytime I update it. So, just in case...
Resurrecting this thread as I discovered something about Apple Music iTunes Match that I did not know...
Initially, when iTunes Match was introduced, I understood that the service basically took your Apple Music library that included songs from CDs, and made them available on every Apple device...