If you find that you can wiggle or spin the DC power cable and loose power at the controller or at the DC motor ports what we've found is a vast majority of the time this can be solved by 'pinching' the male side of the DC power connector. Don't go crazy, obviously we don't want to 'crush' the connector, instead we just want to narrow the inner race of the connector so that it 'grips' the center pin on the controller side better. (video: https://vimeo.com/152983980#t=3m43s )
I seem to have this issue, but I haven't tried the solution yet...