Low Pass Filters. They prevent undesirable resonances with the effects. For example spring gain. Depending on the length of your extension, the weight of your grip piece and the gain setting. The stick can become a pendulum that violently throws from one side to the other when left alone instead of centering...
Or with too much friction, you may feel the stick vibrating in your hand even without moving it, etc.
The adverse effects can be manifold.
There's a LPF for every effect.
First I would deactivate every Effect except spring and see what happens. If you still have the grinding, change the LPF gradually and see if it has a positive effect.
You can always go back to default. If it gets better, re-introduce one effect after another and do the same if.
In general - friction, inertia and so on should be used sparsely.
Btw. can you post a picture of your settings?
