i hate my distributor

this is the 5th time this has happen to me I dont understand why.

always on the freeway this happens to the first 3 time the screw that holds the rotor on my distributor falls off.
then I put lock tight on the screw and the next 2 times the rotor falls apart. this happens once a year has this happen to anyone?

2010-06-25_14.14.09.jpg