Motor imbalance

Good morning everyone,

I’m new to the forum but have been following it for a long time.

I have a problem on my Quadcopter that I can’t find a solution to.

Let me start by saying that it is absolutely symmetrical and balanced. It is made up of a square frame in classic X configuration and whose CG is exactly in the center where the FCU is positioned
The motors are U8II 85kV
Furthermore, the motors are aligned with a digital dial gauge and are EXACTLY vertical on the arm

The whole system weighs about 12kg (including 2kg payload) but I often get “POTENTIAL THRUST LOSS” messages without understanding the problem

From the analysis of the log it emerges that motors 1 and 2 work at PWM of around 1600/1700 while motors 3 and 4 are at 1400/1500 and I repeat that they are all perfectly aligned. Also no balance problems.
Even with payload and batteries, if I hold it with two fingers on the X and Y sides, it is perfectly balanced

I don’t understand why I have to tilt motors 1 and 2 (as the manual suggests) if I really have everything in balance. I would also add that I have done an autotune on the Yaw several times but the result does not change

Could it be a motor tolerance problem? for example some motor that runs differently and therefore 1 and 2 have to compensate?

With Cube Orange I also calibrated the ESCs but even in this case I didn’t understand whether with U8II and Orange the calibration makes sense or not… there are those who say yes and those who say no.
In such a complicated, delicate and expensive sector, it would be nice to have unambiguous opinions

Thanks to anyone who can help me