If your pitch/mod stick is not behaving correctly, for example not sending out the correct values, you should try re-calibrating it. You are also required to re-calibrate the pitch/mod wheel after upgrading to OS version 2.1.07.

To calibrate the pitch and mod stick:

1. Centre the pitch & zero the mod.
2. Go into Global, ensure that 'Mem Protect' is set to Off.
3. Scroll up to the 'Cal Pitch/Mod' page. Re-calibrate the pitch and mod wheels by moving it up down left right. 
4. For Mod,  the max value is 127 and min value is 0. 
5. For Pitch, the value to the left is 0, centre is 128 and to the right is 255. 
6. Press 'write' to save this settings.