Have you updated to Build 634? Yes

Does this happen on any other song? No . . . but, see below

Does this only happen with that style (_CONTACT)? So far, yes. Tried briefly with some others & this didn't occur

Is your tempo at or close to 85 bpm? Interestingly, yes.

Is your time signature 4/4? Yes

When you say "all chords have a rest", exactly what does that mean? No sound? Does each chord appear with a single period after it? Each chord has a single period after it.

I've now realised this occurs after I've defined a Sub-style c/d and changed to one of those two styles. After I click Generate and play every chord will be set to have a rest (a single period after the chord letters).