So it drifts sideways or it starts to flip over if you apply more throttle? If it is the later, I have had the same issue caused by props on incorrectly, motors spinning the wrong way, and a bad gyro thinking it was upside down. I would look at those first and see if perhaps it clears it up.
I figured out what is the problem, but I could not figure out how to fix it.
It's the transmitter!!
I figured it out when I reversed the "AIL" in the transmitter, then the hexa started going to the right instead of the left like before. Then I tried many different settings, and some seemed to affect the behavior of the hexacopter, but I still could not get it right...
I don't know how to properly configure the Turnigy 9X Transmitter! I goggled it, I watched videos... so far, I could not get it to fly straight up...
Maybe I need a fresh mind, tomorrow I will fiddle with the transmitter settings again.
Did you fix the problem Michael? I had a similar thing with a KK V1 board, gave up and bought a KK2.1.5 which seems to be working. It's not trim on the the Tx was it? Will it definitely flip, ie. have you tried holding it or moving it around on a table to see if the correct motors respond, attempting to level itself?