all of them or some of them? were there any busted off EX bolts in the heads did they fix them? sounds like they drill and tap thru the jackets or some one used to long of a EX bolts and busted thru in to the jackets ? any case it a ez fix clean the threads good you could try a hi heat sealer on the bolts or run short set screws down the ex bolt holes and use a welding rod to check the depth of threads and make sure the bolts do not bottom up on the set screws you need to use sealer on set screws that should stop it