i haven't owned a shuttle in quite a few years but never had a problem with the dampeners till they had quite a number of flights on them, say 40 or so flight hours or 200 flights. the shuttle wasn't the best suited for 3D flight so they last longer then they do on other aggressive flying birds. you may want to make sure your have them oiled so the feathering spindle is able to move in them. this is a VERY common problem with shuttles and often they'll hinder the free movement of the main grips. take the links off your main grips and make sure they are free to turn without any restriction from the dampeners if they are, then remove the spindle and oil it and the dampeners and then reassemble the head.

kc