There are several documented cases of lock failure, specific lock failure, in this forum. The flag bounces from extreme recoil, and overcomes the spring that opposes it.

Especially prone are the alloy-framed lightweights in .357 .
If you have seen the tiny piece of wire spring that is designed to keep the flag from bouncing on recoil, you would be amazed that it doesn't evaporate from rust if a damp breeze were to blow past.

I removed the IL parts, all four of them, non-destructively from my 649.

They were a menace to my own safety.