Fly away (almost)

[slup]

... and by the way how come it can fix itself, after like 30 second

It's mainly 2 ways for that if the AC don't crash before ... either the flight controller gives up & drop the positional confidence to 0 & go in ATTI mode. The other possibility is that both gyro & compass slowly feed in corrections & over some time corrects the wrongly initialized IMUYaw.

by the way almost all my flights are hand launch or launch from concrete surface...

The critical moment isn't when you launch ... it's when you power on the AC. It's then the IMUYaw initializes to the compass direction ... so if the compass is deflected there, the IMUYaw will be wrong.

Power on the AC in your out stretched hand (without watches or other magnetic objects) once fully on & the liveview have appeared in the app ... you can safely place it on ground for take off.

 

[Meta4]

I agree to what you say, but i never have this problem before with all my other drone, i think the owner of this post might have experience the same thing because it also goes in a curve.

and by the way how come it can fix itself, after like 30 second

The difference between getting/not getting a yaw error could be a matter of a very small difference in positioning the drone.
You can't tell when you place it where the steel is close to the surface or where there might be a larger bar or an overlap area.
You can't tell if the compass is in the middle of a square or a crossing point.

The amount of deflection varies as well.
A bad yaw error, with a big deflection means the drone is completely uncontrollable and zips off at high speed, usually crashing hard before the flyer can react.
A small yaw error with a small deflection angle is more gentle and semi-controllable.