Kioti CK4210

So I’ve picked up a new second hand wood chipper. This thing is a beast and really puts my Kioti ck4210 to the test. It can chip 6” logs and has a hydraulic feed. Now, to my issue: when using the hydraulic feeder, the two rollers appear to have vastly different amounts of power. The bottom roller does 80% of the work and doesn’t slow. Whereas the top articulating roller can be slowed or even stopped under minor load which messes up the whole feed operation. I’ve also noticed that the roller speed, when adjusted, makes no difference (could be related?). So my question is, how can I send more power to the top roller? Any help would be appreciated!