I've noticed that when the screw holes are drilled and the mounting screws are in place, in time moisture can penetrate into the screw holes and expanding the wood around the screws. The screws can oxidize from the moisture in the wood and become rough and pitted. When you try to remove the oxidized screw out of a tight hole the friction heats the screw making it softer and it breaks.
I learned an easy solution years ago from master builder Phil Kubicki to help reduce the problem. He would simply dip the threads of the screw into a paste wax to reduce the friction, seal the drilled hole with wax to reduce moisture from rusting the screw. I always thought that was an easy simple solution to help prevent screws from rusting and breaking in half when screwing in or out. I do the same on my pickguard and other mounting screws. Always make sure you have the right size drilled hole for the size of the screw you are using. If the hole is to small the friction will heat the screw making it softer and eventually breaking.