wrote:
wise old mechanic taught me that putting a little valve grinding

Remove all traces of paint and grease from the phillips drive screw
heads before trying to remove them. Use a new quality driver.
Degrease the surfaces where the driver must grip. Paint makes a good
lubricant that can cause the drivers to cam out unfortunately.

On reassembly (hopefully with new screws), use anti seize on the
threads, but dont get any near the screw heads.

From an old motorcycle mechanic............