Andy:

I can't replicate your problem.
I opened a "New" BIAB file, enabled the SINATRA.sty style and entered the chords as you described.
The single dot after the 2nd F chord indicates to BIAB not to play anything on that beat.
There shouldn't be any sound on that bar at all, including drums.
If the other 3 shots sound OK, perhaps it has to do with the sound card???

Can you try your 4 chord sequence in a New file with the same style and see if it's the same?
I suppose you already tried:
- shutting down BIAB and restarting
- shutting down the computer and restarting
- doing a BIAB "Return to factory settings"

Let us know. Someone here will be able help you through it.
Good luck!

LLOYD S