First of all My escs and radio were calibrated.
At startup randomly one motor does not start after about 3-4 three minutes successfull run.
If motor starts there is no problem it continues to start and spin.
On my video look at startup, 2.07 and 3.00.
My Quad config is:
Pixhaw with Arducopter 3.2.1
H4 Aliena 680 frame with Aerialmob landing gear
TM-MN4010 370Kv Motors
RCTimer 15x5.5 Propeller
16A Gens Battery
3DR GPS Kit