Optical flow calibration issues

Hello Team,
I have done inflight optical flow calibration as per the documentation. The performance of the drone was stable more or less. Here are my queries regarding it :

  1. The EK3 position source changed to optical flow. If I set the mode to Loiter, a pre arm error is showing " Need position estimate". if i lift the drone to few cm up from ground, then it will be Ready to Arm. Later, the performance of the drone was good.
  2. (Continuation of above point) During the flight, If any pitch or roll inputs are given, the drone responds but the drone comes back to where it was hovering.
  3. (Continuation of above point) When the mode was switched from Loiter to FlowHold (indoors) the performance was unstable.
  4. If the mode is set to Flow hold, the moment the drone takes off, there was erratic altitude changes and the flight was not stable.
    Here are the logs are attached.
    Thanks.

Quad specs:
Optical flow sensor: PMW3901
Lidar: TF-Luna
FC: Matek H743-mini
Motors & Props: 6 inch props, 1504 3000kv motors