bottom 4 pads not respondin like they used to

pads 1-4 work but at an angle that only i can get to work when loading and saving.. anyone 1 no where i can get pads fixed and/OR upgraded making all pads more sensitive like the 4000s? (sensitivity is all the way up on the bottom 4 pads n its still horrible, iv had to just program all banks from 5-16..)

OR any videos on hot to do it myself... googling it now..