FX Impact probe screw stripped

Maybe take the gun partially apart after degassing. Then you can take the screw that holds the block that the pellet probe slides into out. Then should be able to rotate it and get it out. Vise grips or something might bite onto the stripped screw after out of the gun.

Make sure you heat the screw first or the other can be stripped also. Make sure youre using the correct size metric hex wrenches.
 
Earlier Impacts had a small screw that frrequently froze up when removing. That happened to me. I had to take the sideplate off to get the probe carrier out. Later, they changed to a larger grub screw requiring a different probe carrier. You can see the parts changes on the FX website. Go to the Impact parts list. I would harass them to give you a new carrier and screw on warranty even though the gun is outside the warranty. This is definitely a design mistake.