try doing a "clean file properties" on the album tag for one or some of those album(s). you particularly want the convert to single spacing and remove trailing spaces options ticked.
For a multi-artist album to be recognised as such by MC, all the files must be in the same directory, have exactly the same album name and different artist tags.
For the album to be complete, the tracks must be numbered sequentially from 01 to the highest numbered track.
It is possible to force the issue by selecting an offending album and setting the [album artist] tag to (Multiple Artists)
with the brackets. This will work very well for re-grouping those files in different artist based folders back into a single, album based directory.
I wonder if you are dealing with muti-disc, multi-artist albums? many of them are.
If you are, and you are keeping all the files in a single album folder, number each track correctly on each disc, then use MC's [disc #] field to handle presentation in the library, this all works very well, except for the fact that it breaks the [complete album] rule into the bargain.
It's why I incorporate a [disc #] directory in my rename from properties rules.
-marko.