I've had the same problem.. I found the Pro3 actually sends that out as midi as well. I contacted support about it, and I think I ran out of patience before trying the suggestion:
You can try reversing the polarity in case your expression pedal has different wiring schemes. In Pedal Function there are two settings: LPF Full and LPF Half. With LPF Full selected, the pedal is set to control the full range of the filter cutoff frequency. If LPF Half is selected, the pedal will control only from closed to half-open. Please try changing those and see if you notice a difference.