I found it. It isn't a bug after all. If you go to Options/Preferences/Notation, there's a setting for max ledger lines. It defaults to two -- which wasn't enough with the music I was reading through. I set it to four and now my high notes are reading out the way they should. What's curious is this "control" had no effect on ledger lines below the staff. They would plunge as far down as they needed. Oh well, I'm glad I found this little control.