Those two problems are not unheard of with some Whites, the spring can be replaced, the nipple on some guns is a little too large and the caps don't go on far enough and that can cause missfires. Not a big problem, you can either try a differnt nipple and see if it works better, maybe the one from the UM. If that fixes it either get a new plug or sand or file down the outside of the nipple a little at a time untill the caps almost bottom out on the nipple, some times just a good push on the cap to make sure it is seated on far enough will do the trick, a flat screwdriver works good when at the range. I have gotten into the habit of making extra effort in seating the cap on my guns.

Hope that helps.[8D]