Unifi ac pro very low signal

Hi guys, I have 2 identical unifi ac pro which I flashed with 21.02.0-rc3. Everything works fine, however one of the unifi provides very weak signal on both radios. I can connect to it only in 30 cm distance. The other is perfectly visible from another room 15m away. The power settings is 24dbm on both. What is the problem and is it possible to fix it?

Thank you, Dmitry

Flash back to stock to confirm it isn't a hardware problem.

I did, the same thing. Is it possible that some nonvolatile settings, that the system is using to calibrate the output power has been destroyed somehow? There are no signs, that something has burnt out. And there is a correct wifi signal, even it is very low.