Most, if not all EX's, have a what I'll call a swivel tip. They should be serviced on a regular basis, it doesn't take much to keep them working the way they should. To service them, use a small pair of pliers to first twist the tip around while it is in place. Once you've twisted the tip to make sure it is moving freely, use the pliers to remove the tip. After the tip is remover, use a fine pointed needle tool to clean out the hole the tip sits in. There may not be anything in there, but, it doesn't hurt to make sure there isn't. Now, it's easy to reinstall the tip into the screw, but, before you do, you should lubricate the small shaft of the swivel tip. I use a graphite grease to lube mine, and I've never had a problem with any of the screws or tips. I'm of the opinion that everything that moves on a machine should be greased, that's why I started greasing the swivel tips on my saw.
Len