I'm playing on the Wii version, just in case this is an isolated issue.
So I'm going back through Story to five-star all of the songs that my wife and I missed. I'm not playing anything new, just stuff that we've done. Well, my star total is 279...but by my math, I've only achieved 275 stars. I've double-checked the venues, and it's only 275.
Where on earth could I be missing stars?