Issue with MPC One While Overdubbing To Track

I've got a question about my MPC One. I'm a very new user of the unit. I've noticed that sometimes when I go to record multiple pad sounds to a single track, I am not hearing some of the triggered sounds play back or succesfully record. I filmed an example of what I'm talking about.

In this example, I recorded the hi hat to track 1. I'm now trying to overdub the snare from the same program on top of track 1. The snare pad lights up, and sometimes I hear it during the overdub process, but then it does not sound when playing back subsequently. It looks like the track is 'red' for 'armed.' The snares show up visibly in grid mode. They do not make a sound and they are completely silent during playback.

I'm on firmware 2.10.1

Does anybody know what I'm missing here? Sorry if it's something obvious. I'm a newb with this unit. Thanks in advance.

Chopped programs are automatically set to monophonic playback. This works well when region chopping but is not so great if you have chopped down to individual hits and need to overlap chops. To fix this go to PROGRAM EDIT > MASTER and in the first column change 'POLY: Mono' to POLY:Poly.