This is most likely a metadata issue and not an MM malfunction, but some details are needed.

Is this disk 1 of a multi-disk set?
What is the disk?
Is there a release of the disk somewhere that doesn't have the last 4 tracks?
What metadata source are you using?
Is the album artist for the last 4 tracks the same as for the other tracks?

So using the auto lookup, MM5 says this is not Album (Disk 1) It's Album.

This is fine, it's technically correct. But what it doesn't do is pull in the disk number if it does that.

I'm also getting 23 tracks of an album fine, then it will say these last 4 are 4 completely different albums.

These are all ripped from the same CD, and I've even done it again to make sure.

Bug?