EKF3 Yaw Inconsistent / Optical Flow

Attached are the logs for a flight today:

No GPS.
Arkflow Optical Flow (mounted 90 degrees clockwise on x axis, flow orientation is 900 in parameters).
Drone was launched in loiter mode about 30cm off the ground.
Drone hovered for a minute but yaw inconsistencies started to build up toward the end so I landed it. Tried it again and yaw inconsistencies varied from 170 degrees to 30 degrees.

Potential causes/concerns:

  • Taking off in loiter mode and so close to the ground might not be a good enough position estimate and the yaw inconsistencies build up over time?
  • Poor mounting of the Arkflow (vibration)?
    *Magnetic interference?