Weird possible brown out?

Doing some test flying today, my tri randomly fell out of the air. As far as I could tell all of the the motors simply shut off. Luckily no damage was done but I would like to resolve the issue before I head to higher altitudes. My setup is a clone apm 2.6, powered solely by the power module. I have had a little look at the logs, and as far as I can tell the apm simply stopped the throttle to the escs? Any help would be much appriciated…

Geck