Do you still have this problem if you push the pedal far enough to compress the rubber stops when you calibrate the pedal?
Not sure if you are asking OP or me, but anyways I will post my answer.
I would say that pushing the pedal far enough to compress the rubber exactly causes this problem, because it forces pot to value which is beyond normal pedal range. Kemper gets this out-of-range value and makes it new MAX. but is is NOT MAX of normal range. I came to one possible hardware workaround: take the rubber stops out and replace them with uncompressible material, so the pedal would not go out of range. But then we will loose ability to use the switch. I would really like to see how the Mission EP1KP is set up because it's construction is the same as my pedal - VOX/CryBaby. And they use the switch also....