Brand new APM 2.6. Flew 1 minute and decided to land

Just want to ask if there is a known issue with firmware 3.1.5 before I started changing hardware. Brand new APM 2.6 (My second one. I have another one on the old firmware that is flying fine). Everything set up as I normally did. On a quad X with AXI 2814 motors, Mystery Blue 40 amps speed controllers. SimonK firmware. 4 cell battery pack. Using PWM FrSky receiver. No failsafe what so ever. Calibrated compass, accelerometers, speed controllers, radio. I was using a Castle Creation BEC to power the receiver. I also have a three wire cable from channel 1 to the APM 2.6 input. The APM 2.6 will not arm with the Castle Creation BEC connected. So I unplugged the BEC and let the APM 2.6 to power the receiver and it armed just fine.

Power up no problem. Took off in stabilized mode no problem. Flipped to loiter mode and it stayed there no problem at 30 feet altitude. In less then a minute the machine twitched once to the left and motors slowed down and landed itself.

Motors and speed controllers work fine while connected to the receiver directly. So no problem there.

Please provide some intelligent suggestions as to which parameter I should check. It may be a very simple issue that one parameter is enabled inadvertently in this latest firmware.

FWIW, I had a similar issue with my Pixhawk also. That could have been a totally different situation since the PixHawk eventually died.

Please don’t blame the machine or the motor or the speed controller. I have been building and flying hundreds of multi rotors. This is not my first machine nor my first flight controller I am setting up. I like the APM 2.6 because I have one that is very reliable. I could have bought another Pixhawk but the APM 2.6 is proven to be more reliable at this point.

Thanks in advance.

Please ignore the above post. It may very well be a bad speed controller. I will continue to trouble shoot.