98 winstar camshaft position sensor

Hey to everyone.This is my first thread.Glad to be here.I have replaced the camshaft position sensor on my '98 winstar twice.Each time the insides get torn up.The shaft lines up just fine.Has anyone else had this problem?Do I need to replace the shaft? Runs fine until it tears it up, then it begins to buck and jump. (And yes, I'm from the south,Memphis,Tn.as you can tell by the way I talk.) Would appreciate any help.Thanks,Johnny (wizardman01) ps winstar limited 3.8