Matrix-6s are prone to wonky levers. 

As for the Pitch Bend, one of the things that I found which helps immensely is to go to the MASTER menu, item #52, or CALIBRATE.  I work my PB lever back and forth a couple of times, letting it self-center, then do the READY / YES on the keypad.  Doing the calibration routine sets the VCFs' response, Pulse Widths, some other functions... and the Pitch Bend lever's response. You may have to do the CALIBRATE routine a couple of times, but it should at least help a bit.

As to the MOD lever, I'd bet that it could be mechanical.  Perhaps the lever isn't rotating the MOD pot's shaft, or it may be a broken wire or a dirty or loose connector, or a bad solder joint.

Best of luck with your upcoming detective work!

Dave Garfield