> MB will only play the first song in a group of tracks
I experienced something like that when my NAS went offline and then came back; MB seemed to have detected that the NAS had gone, and therefore the media was unavailable, but, if forced to go look for a track (by manually advancing or selecting), it was able to find the track and play it.
Are tracks in 'Now Playing' showing as unavailable? (greyed out, IIRC, with a yellow '!' caution triangle next to them)
The answer for me was a library re-scan. Or maybe shut down and re-start MB after the NAS came up again.