Hello!
I have been facing problems regarding sensitivity with my Dunlop DVP4 Mini expression pedal and my HX Stomp XL.
In the video below, I demonstrated how practically 40% of the pedal's expression does not work.
I noticed that with the volume block, the sensitivity is better than with Wah blocks. With the volume block, I can cover about 90% of the pedal's sensitivity.
Note: Inside the DVP4 Mini the key is EXP.