IF the shift pin isnt located properly, it can cause this.. so can a wore shift shaft and so can shift forks. so many variables hard to tell which it could be. Id start at the shift shaft and the locating pin. And do the mod on th star, helps a bunch and easy to do. You CAN run throught he gears with the side case off, with a screw driver and a buddy spinnin the tires, to see how she works as far as trans go, to see if its not internal without splittin the cases. should be able to shift it. If not, could be forks. Also curious, how far do you have to throw the shifter up to shift at low speed? Also check the spring on the shift shaft make sure its good. They are cheap