Have you been removing and replacing the screws, allowing the heads to come and go through the pad? If so, that's a no-no. Use every precaution to treat the slits as tenderly as possible. Use a small diameter shank, keep it lubed, and tug on the pad as you back out the screws, alternating from one to the other so as to keep the heads buried. The way those slits are gaped suggests they may have been passing large objects....
....reminds me of the guy who got kicked out of the tavern because his pet monkey disrupted a pool game and swallowed the cue ball. The next week he convinced the bartender the monkey would behave and they were allowed in. A patron gave the monkey a peanut and the monkey promptly shoved it up his butt, pulled it out and ate it. Everybody thought it was disgusting and the bartender was about to kick them out again. But then the guy explained, "Ever since he swallowed that cue ball he's been sizing everything before he eats it."
