Motor only working when channel assigned to function "Motor 3" in QGroundControl

Drone is not taking off at full throttle and wants to flip onto its side. Currently performing a root cause analysis and trying every combination of motor, esc, channel on the flight controller, and motor assignment in QGroundControl. Currently, every combination of motor, esc, and flight controller channel works individually so long as “motor 3” is assigned to that channel in QGroundControl. Conversely, every other combination audibly decelerates when connected to a channel that is NOT assigned to “motor 3” in QGroundControl.

Any thoughts on how I might address this problem? Is my flight controller cooked?

HolyBro 650X with pixhawk 6x