Had this same exact problem w woodcrafts on my gen4. Every angle was as close to perpendicular as possible, it would shift through the gears but it was so dam hard compared to the attack rearsets. I ripped apart the gearbox multiple times trying to figure out the problem before I narrowed it down to the rearset and not the gearbox. Went back to the attacks and problem solved. All the pivots in the rearsets were freely moving and everything, such a weird problem.