Hi I am new to Quadcopter. Recently, I built a F450 frame quadcopter with APM 2.8 and I use Mission Planner 1.3.45 with ArduCopter firmware V3.2.1. I do a motor test, all works for me except test all in sequence. When i test all in sequence only the first motor (top right) spins, then nothing happens after the first motor stops. How can I fix that? Thanks in advance!!!