Went for an initial run about 2 hours ago and got the same symptoms as you. The Motor will stop accelerating and cut out at about 1/2 throttle if i jab the throttle fast, I need to slowly accelerate for it not to cut off power. This is with using the flightpower 25C 5000mah battery so I dunt think quoality of battery packs should come into play.

seems like the cut-off algorithm is super sensitive or wrongly calibrated?