OK, I have found a solution (I think it helped).
Resistance work as it should and I use only Bluetooth pairing.
Post by [Michael] (Michael_Latsch_DLH):
I recommend that you delete the prefs.xml and knowndevices.xml files from your Zwift folder. These files store your in-app preferences and information about devices that you’ve previously paired. Occasionally, these files can hang on to incorrect information, such as a wrong trainer selection, or a device paired in the wrong spot (e.g. a speed sensor paired in the cadence spot).
Modifying the files in your Documents/Zwift folder can also have unintended consequences, from your avatar appearing on the wrong course to display issues, or being unable to pair your devices, and is something that we generally don’t recommend. When these two files are deleted, they will regenerate fresh copies the next time you launch Zwift.
Here’s what you’ll need to do:
1. Exit and close Zwift. Make sure Zwift is closed from your your dock as well.
2. Open the Documents folder on your computer.
3. Open your Zwift folder.
4. Delete the files named prefs.xml and knowndevices.xml, then close these folders.
5. Launch Zwift again and pair your devices in the correct spots on the Zwift pairing screen, then go for a ride.