Rangefinder scaling not working


I’m trying to get the ultrasonic sensor running for landing maneuver.
I managed to get an output. Unfortunately, the output is not scaled correctly.

I had no success to fix the scaling by doing the following (absolutely nothing has changed):
Trying many different values for RNGFND1_SCALING.
Trying to guess an offset and set RNGFND1_OFFSET.
Setting RNGFND1_MAX_CM & RNGFND1_MIN_CM to the correct values according to the data-sheet.
Trying different RNGFND1_FUNCTION settings.

Ultrasonic sensor: JSN-SR04T
Flight controller: Omnibus F4 Pro
ArduCopter 4.0.6

Do you guys have any suggestions for me?
It seems to be a software issue, cause when I take measurements real height is proportional to the measured values.
So there is a linear connection between real height and measured height, but the scaling it off.

Let me know if you need more information.

Best regards