the same thing happened to 4 of 6 screws on a spider diff i ordered for my buddy. i decided to leave it alone because he has had real bad luck with everything (r/c related) he has put his hands on so far. if he decides to pursue it further, i am going to cut slots in the screws with my dremel so i can get the screws out with a flat-head screw driver. unfortunately, that grease in the center diff pretty much makes the buggy front wheel drive.