I noticed the same problem on mine. If you don´t mind replacing the bolts when you´re done, use a Dremel or similar rotary tool to CAREFULLY cut a slot into the head of the bolts, then put a flat-blade screwdriver into the slot and *gently* tap straight in a few times with a hammer. The idea is to loosen any crap stuck in the threads, and if applicable, to help reform any damaged threads. Use the bigger flatblade screwdriver to lever the screws out and replace them with some nice, shiny, stainless-steel hex bolts.