Devo 10 and Baseflight calibration problem

I'm trying to setup my first ever quad. I have a problem with the radio calibration in the receiver tab in Cleanflight/Baseflight. When trying to adjust the center value to 1500, I have to press subtrim a lot of times before the output changes. And when it does, it changes from lets say 1507 to 1494.

I have a Devo 10 transmitter with deviationtx firmware and an OrangeRX R410X receiver hooked up via PPM to the Naze32 FC.

Can anyone help me solve the problem?

Thanks!

..with a RX615X too...
Simple answer, it has not to be equal to 1500. If the midpoint is e.g. 1507. it is ok.
Calibrate the sticks and even then there are not the same values on every channel.

But a question about your rx. Does the order change from TAER for pwm to AETR for cppm as with my 615?

What bugs me is the large jumps in cleanflight. I have confirmed from others(with different radio systems) that they can trim the center point accurately. Is this a limitation in the Devo 10 or in the devention firmware? What is the resolution of the output in dsmx mode?

I can confirm AETR for cppm mode.