Wacky chords, suddenly

I'd almost finished this lead sheet when suddenly, for no apparent reason, the flat signs in all the chord symbols changed to "e10d".

I could double-click a chord and see the original change—but as soon as I exited the edit (Esc), the misspelling returned.

EDIT: I've subsequently opened and closed it a few times (exiting MS each time), and now the chords appear normally! In case the attachment has some internal code that might explain the quirk, I'm posting it here anyway.