Calibration 2: Per-Scanner RSSI Offsets doesn't work for me

I have a handful of mini esp32c3 boards. So I used one of them for the reference pair in calibration step 1.
That works great. Once I found good values for the reference power and attenuation, all these type of scanners showed similar results (I calibrated at 1 and 4 meters)

But then I started to calibrate the deviating scanners in step 2 (Athom plug v3, Apollo Air-1, Shelly gen3 mini).
For example the Athom plug, I started to adjust the RSSI at 1m (settled around -18). Then I verified the distance at 4m, but measured around 1.4m!

So I guess step 2 should allow to adjust the attenuation per scanner as well in order to get this right.

Note: orientation of both the device and scanner influence the distant substantially (2 times easily). Guess that is a given, so used the same orientations in step 2.

Best Eric