Hi Jeremy,
sorry your forum entry did not come to my attention until now.
Ok, I understand the problem, instrument 1 does not play on the 3rd track.
To my knowledge there is no known bug at the moment.
Just to make sure you know this feature, there are track mutes, as well as instrument mutes. That means, an instrument can still be muted, even when the track is not.
Instrument mutes are the two button rows on the top left. If the first button is lit in mixer mode that would mean instrument 1 is muted.
I will try to reproduce it the next days, please keep me posted here if you make more observations.
Cheers!