Hi axman53,

The Intensity sets the Q (resonance) of the Wah filter.  What you want to do is assign the expression pedal to the Speed knob.  You will need to unassign it to the Intensity as well.  When you set the waveform to envelope, this Speed knob becomes SENS, which adjusts how sensitive to input the envelope follower is.  At SENS of 0 the touch wah effect you want should be shut off.  You should experiment though to see what maximum value of SENS works best for your setup.  

So basically there is no bug.  I believe the MF is already capable of doing what you want. 

-Russ