If I unfreeze and regenerate it does generate the entire length properly. It's strange, what I reported before about being sensitive to time before playing (warm up) and whether I'm in chord view or track view. Track view and allowing time between opening the song file and hitting play seem to correlate with it working as expected. As soon as I hit play though, it stops generating the drum (and sometimes other) part (as I watch it in the Tracks window). This is one of the reasons I freeze tracks, so I don't have to wait for generation and can play quickly.

On the song where the drums are out of sync, unfreezing and regenerating does not make any difference. Drums remain out of sync, as if they started playing a half measure too late or are at a slightly different tempo. The particular song uses 3 style changes, but not a multistyle. It's also sensitive to where I start playback. If it is at the start of the second section, it plays fine. If it's anywhere else after the end of the first section then sync problems. Nothing I do lets me play back this song as expected. It has been rendered completely unusable after the upgrade.