Gyri,
I think that you can either reduce the throw on the right elev or increase the throw on the left elev by screwing in or out the control horns.
I'm pretty sure that there is some sort of cause to induce an aerodynamic inbalance that is causing the snapping. Perhaps slightly different hinge locations, pushrod stiffness, servo mounting flex, etc......
Remember to keep your neutral point the same. I didn't notice any other difference in flight due to the purposely mismatched elevators. But I need more time.
If your adjustments don't work, just undo it back to where you were.
Good luck.