DJM S7 midi mapping browse button in Serato dj pro

for some reason the left side browse button doesn't work to scroll up and down through the library. If you press the button however, it does switch between the crate library and track library. On the other hand the right side browse button works fine. Anyone have any tips to midi map the left browse button? I tried the serato dj pro midi mapping function and couldn't get it to work...