i had the same thing happen to my tribute. i could remove the top screw from one of the mods but not the bottom. i tried everything and stripped two allen wrenches in the process.

i finally got it by applying penetrating oil (and also some wd) and heating it on the electric stove burner. i noticed on mine that i could "rock" the screw a little by moving the top of the mod where i had taken the top screw out. theres not much possible movement due to teh design but i could move it back and forth a little. i think the beveled out portion is where they get stuck, not the threaded. otherwise i would not have been able to rock it like i did.

now i put string wax and check em every few days. they have been working a little loose but not sticking anymore.
hope this helps.

insatiable