Pixhawk Mini engine problem


i use a quadrocopter with a Pixhawk Mini FC. After I have completed a few halfway satisfactory flights the following problem suddenly appears:
After arming all engines start normally. Although I accelerate, after a few seconds one or two of the engines lose speed and finally stop. The others continue to run normally.
Sometimes the following error message appears before arming:
“Preeflight: GPS Horizontal Pos Error to High”
Compass and the other sensors I have of course carefully calibrated.

The used board is a PX4 FMU V5. The PX4 firmware is cleanly loaded I think.
Here is the path when downloading:


Does anyone have an idea?
Say thank you

Best Regards Hermann

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i have solved the problem. After I recalibrated the ESC’s the motors run cleanly.