Unstable Yaw - Quadcopter (ext mag x w/ opt flow)

ArduCopter Copter 3.6
1

Hello,
I have build a quadcopter and having some issues with yaw when in loiter mode. I am running the following:

1 - Navio2 board
2 - TFMini for elevation
3) - PX4flow
4) - External mag sensor

I have attached my flight log for review. This is me taking off in loiter mode and not touching the controls.

The copter seem stable for a few seconds, then it starts yawing +/- 15deg.

This is an indoor flight without GPS.

Any thoughts on what I should look for or check in my logs?1 12-31-1969 6-00-00 PM.bin (872.8 KB)

2

its seems that this craft is not tuned.
do you auto tuned this craft ?
http://ardupilot.org/copter/docs/tuning-process-instructions.html