Music imported from CD disappearing

I've had this problem for a while but always just re-imported the tracks. Now I am certain that some of the tracks I imported from CDs have disappeared from iTunes. I see from this forum that this is a long-standing question but none of the suggested solutions seem to apply.

I import (and purchase) music for iTunes on my Mac and then use iTunes Match to get the music on other devices.

Tracks I know I have imported and have looked for are no longer listed on iTunes on my Mac or available on devices through Match.

For example I imported three tracks form an album several years ago. I searched for and found the correct artwork for that album which I associated with the tracks.

Now only one of the three tracks shows up on iTunes and with different artwork for an album I have never owned. Most of the rest of my music seems OK but from time to time when I search for a particular track I come across the same missing track problem.

Does anyone know what might be going on? Clearly I can re-import the tracks but this random and unpredictable behaviour seems to destroy the point of having my music collection in iTunes. Is this a known problem with iTunes? Maybe it's associated with the latest update, I don't know.

I appreciate any ideas other might have to sort this out.