Why does iTunes Match match only some songs from the same album?
It's been confirmed elsewhere that metadata alone will not give success in matching (if it were, someone would quickly find a way to just create thousands of dummy files with the right metadata). Some audio fingerprinting is going on, and you can test it by changing the metadata of one track to that of another one, and see if if matches the audio or the metadata. Still, metadata plays a role as well.

MacWorld have a note on the problem of one or a few songs not matching from an album:  Basically, it seem to affect specific songs (rather than just randomly failing every n:th song). Two possible reasons for this:


The audio or metadata specific to that track confuses the matching algorithm (as we know, audio fingerprinting is not an exact science)
There is a rights issue with particular tracks that Apple haven't been able to find agreement for.