Over the years I have had this happen a few times. Take an extremely sharp pointed center punch and place it near the stripped area at an angle and tap the center punch in a counter clockwise direction.
Don't laugh, but when I built my first one, I launched the spring and detent twice. Then I went to my closet and got a clear dry cleaner bag and built it while it was inside the bag. Didn't loose any parts!
I find a utility knife blade handy while assembling the end plate/castle nut arrangement...