Need help figuring out how this valve got bent like this

[f4udriver]

I am not the most experienced engine guy in the world but I can't figure out how this could of happened.

LS7 Dry sump
C5R block
All pro heads

I had been fighting backfiring issues and poor performance for 4 years. I replaced the plugs, removed the remote coils and installed new ones, removed the Harrop intake and put a stock unit back on, re-tuned the engine multiple times, replaced the plug wires and removed the valve covers to inspect the springs. After 4 years of hell I pulled the engine and had it opened up. One of the valves was bent where you would expect it to be bent. But this valve was bent about an inch from the top.

Any ideasNeed help figuring how this valve (exhaust) got bent like this