I have a Mission Engineering EP-1 too after reading that others are using it fine, I wanted to share my odd issue with it. Connected to the Helix, I have found that the heel position is correctly set at zero but it reaches 100 at midway and then back to zero at full toe position.
Anyone seen this issue or is it me? I have tried the pedal with my HD500x and it works well as expected. I have also changed the cable a few times without resolution. I wishing the Helix as a manual expression pedal calibration setting.