Slimserver was splitting an album into two albums in the browse album list.  I discovered this was due to one track having the disc number field set differently than other tracks.  In my particular case the last three tracks alphabetically were assigned to a separate album (same album title, artist, etc.).  

The seventeenth track (of 19) had an extra tag, "disc number", set to 1. The other 18 tracks did not have a value for this field. So apparently, SlimServer came to track 17, saw the disc number field, and even though all other tags were identical, started a new album. You could argue this is a feature, not a bug, except that tracks 18 and 19, without the disc number tag, were added to track 17's album rather than being lumped with tracks 1-16.  (All track numbers refer to alphabetical track ordering.)