Well, not a horror story, but sure could have been.
During our concert last night I kept hearing my 1st valve spring rattling or clicking. During a break or long rest I loosened the valve's top cap and raised and lowered the valve while twisting it trying to re-seat the spring. This usually worked in the past, but didn't last night. I decided to ignore it and put up with the rattle.
Today I pulled off the bottom valve cap and found a broken 1st valve spring! Sure glad I didn't do this during the concert as I might not have gotten the parts back in to make the valve work again. I had a couple of solos too. Whew!
I keep spare springs at home but not with me at a gig. This is the first time I've ever had a broken spring.