MIDI learn and erratically move from knob

I have a trouble here. I try use my MIDI controller (Behringer UMX250) with Ardour and Charlatan (synth). All works very well except the filter cutoff knob. The UI has a frequency curve different from the generic cutoff control. I can link the “Frequency” knob with my midi controller, but when I touch the hardware Charlatan moves erratically. No 0 to 100, or something that, maybe the knob is logarithmic, I don’t know but that seems to be not supported by Charlatan synth internal UI and that is the reason that not possible mapping the values to a 0.0 - 1.0 range.

Is a plugin error? or maybe Can I add something between my MIDI controller and the synth for move constantly?

Peace.

OS: Debian 13
Ardour: 9.2.3
Charlatan: 3.3.2