Motor Problems after successful Calibration

I have successfully calibrated my quadcopter’s ESC on the Pixhawk and tested the throttle and it works, all motors go on at the same time and increase power as I throw up the throttle.

After I restart the Pixhawk, these settings seem to get lost or forgotten. This is suggested because once I press the safety off, and arm the drone, the motors no longer go on together, 3 of them fire, and 1 of them doesn’t go on until the throttle is over half way up.

I am arming by holding the throttle in the bottom right position until the LED turns solid blue. I have calibrated the RC with Mission Planner already.