kelly controller 144v 300amp khb regen problems

So i have a kelly running on 40s of lipo. For some reason I can't get the regen working effectively. Im using a brake switch, and the symptoms seem to be that i can feel it jerk on and off when i pull the brake. It cuts the throttle until i release the brake, so i know there isnt just a sweet spot in the brake lever sensor, but it doesn't seem to consistently activate regen. I have seen up to 25 amps in regen at 140+v, so when it works it works well. has anyone else experienced regen issues with the khb controller series? i have played with the settings which include a "percent regen on brake switch" setting, which tbh i dont understand; it can be changed from 0 to 50, but changing it doesnt seem to do anything.
Any help is appreciated. my next step will be emailing kelly prbly...

Regen power depends on battery status: if battery is already fully charged, regen will be 0% to prevent damage to battery.
Try experimenting with regen when battery is at 50%.

About how the sliders work, this is how I understand it:
- brake switch regen: it's a "binary" or "on/off" regen, at fixed power which you set once and can't be changed while driving; hence you can't set it too high, because it could result in dangerous immediate slowing down of the vehicle;
- throttle released regen: as above, but enabled by throttle release rather than separated switch;
- brake sensor regen: regen power variable from 0% to 100% depending on analog sensor value, which ranges from 0 to 5V. For testing you can use a throttle pedal, which has same output of a brake sensor. In "real life" you should use a pressure sensor in the brake circuit if you have an Electrical Powered Braking System, or a position sensor in the brake pedal. On my KHB72701 I should wire the sensor output to J2/6 pin, and connect GND and Power of the sensor to GND and 5V pin.

Currently this is just theory, not yet tested.