Have you checked the temp on the MM when this happens? I don't know what the current draw of your setup is, but I had a similar problem with my Spektrum, which was actually worse, because the Spektrum takes a relatively long time to reboot.

As I understand it, the MM will shut itself down (thermal?) for very short periods of time when the esc is bordering on overheating. The problem is that everytime it shuts down (and this can happen a bunch of times in a second or two), the receiver starts the reboot process all over again. I was running 3S at the time. When I went to the ubec, the problem went away.