I believe this is an old bug that I rediscovered and found a workaround for.

Consider a triplet of shots (at a 50% Higher tempo, to get the triplet effect) followed by a return to 4/4 at the normal tempo. You can code it like this:
Measure 1: 3 beats, 220bpm, D..,D.. D..
Measure 2: 4 beats, 140bpm, G..

The problem here is that the G.. will not sound. It seems to be because the last chord from the previous measure is missing. If you have a two beat measure, then the first two beats from the next measure will not sound.

The work-around is to pencil in the missing G.. as the last beat of the first measure, so it reads like this:
Measure 1: 3 beats, 220bpm, D..,D.. D..,G..
Measure 2: 4 beats, 140bpm, G..

The last beat in measure 1 will not play because it is greyed out and is the fourth beat of a three beat measure, but this time the G.. for measure 2 will actually sound. I assume this will also work for those cases where the first two and three beats are missing after a two or single-beat measure, respectively.