Yeah, that's your problem right there. Removing an old Phillips screw will take more (usually much more) torque than it took to install it, so it'll cam out. The problem is that you're trying to get them out. Don't do that. Phillips screws were never designed for removal that way. They were meant to be used for installation only, and to limit torque on installation. If it's been installed with thread-locker, that should be a sign to you that it's never supposed to be removed. If you want a screw that's meant to be removed after years of service, pick something else; Phillips is not designed for this.