What does H stand for in the Plan section in Mission Planner?

That’s a big clue. If you have to force arm it means the drone hasn’t passed all the arming checks. In this case I’m going to guess it’s the EKF position. Could be other reasons.

How is the tune? Did you use How to methodically configure and tune any ArduCopter?

You can post the .bin log file for the flight if you want to get some more specific help with the drone.

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