I have found a large number of projectiles with the fuzes partially unscrewed. Pretty much all U.S. fuzes are right hand thread for nose and left hand thread for tail.
My theory about the unscrewing of fuzes, is that the projectile and fuze are spinning. If the projectile encounters and object, like the ground, at a graze angle, so that the ground slows the projectile rotation without touching the fuze, then the inertia of the fuze that is still spinning unscrews it from the slower spinning projectile. It's physics!