Some algorithm is computationally heavy.

True, but a simple volume control is absolutely not computationally heavy, especially when you have the kind of DSP hardware that the H9 does.

I think there’s something wrong with the way the H9 calibrates expression pedals. I have an Ernie Ball VP Jnr 25k pedal, even with zero effects on and the pedal set to control global volume out, it’s very uneven, and the stepping in the lower ranges is terrible. Fading up from silent kicks in quite suddenly, and there is little change after about 80% up. With distorted (Sculpt) sounds it’s even more noticable, to the point of being completely unusable.

This is purely a calibration problem (or it’s a hardware problem with the A/D converter in the expression input). The same pedal used with a Line6 M13 is totally smooth, fading in gently, and the whole range of the pedal is usable, it feels like an inline analog volume pedal. So it’s not the pedal.

The only help I’ve found on re-calibrating is to turn calibration off and then on again, but this hasn’t made any difference.