Hello! I think the problem were motors 1 and 6 because they were at maximum while 3 and 8 were at minimum. So it seems you had an electric problem in the connection of those two motors (1 and 6) because it would be strange that two ESC or motors burned at the same time.
Check those connections and see if there is something strange in those two motors.
Hi i am having problems with the same poss set up as you. two or three motors spin down at flight settings. i am using the pixhawk 4,
mine weighs 14Kgs, what settings are you using set up any help would be fantastic to get this flying. so far not had much help from the guys on here.
i did what one guy said just get it flying and it will sort its self out. hmmm that nearly cost me a very very expensive copter lucky I had it tethered, only 2 ft off the ground.