I had similar problem on my 2011 and have several recommendations;
1) Be aware that there are two "angle sensors" (at least on the 2011 models there are
). The one that caused my similar problem and I suspect is causing your's is the "Shift Angle Sensor" (~$50). I think the other one was called the "Brake Angle Sensor" and is a lot more expensive (~$80).
2) The service manual instructions had me tear down through the middle of the quad (remove the seat, side panels, air filter, filter box, connecting hoses, etc, etc) to get to the shift angle sensor mounted at the bottom
of the crank case. A real hassle and pretty much impossible to do! After trying for over an hour to reach the two socket bolts with an allen wrench and scratching the hell out of my arms on everything in-between, I finally gave up...
Then I figured I'd take a look at it from the bottom looking up and discovered all I had to do was remove 3 or 4 skid plate bolts, hold the plate down and the sensor was right there, easily accessible! It took 10 minutes tops to change it out, but then another hour to put everything else back together that the service manual had me remove.
Bottom line, that fixed it! It still shifts to never never land ("-") now and then, but turning it off, then back on a couple of times seems to work.