Gyro Crawl help

Hi all,

I am having a bad gyro crawl on one of my pixhawks running v3.5 and v3.6.
I have up and downgraded several times the firmware and still have the issue.

Sometimes it forgets to calibrate at startup. When it calibrates “gx mean:” starts at 0 and crawls to 20-40 within 20 minutes and in rare cases it crawls to about 3-5 and stays there.
All other axes stay at 0.

This is a bare pixhawk on the table without any peripherals, connected to the computer via USB cable. On-board mag calibrates at 175, 504, 143

What is causing the problem?
Is the gyro dead?
can AP 3.x fly with 1 gyro?

Many thanks in advance!

Guys, anyone, any ideas?