What causes light primer strikes

What Is A Light Primer Strike? - The Mag Life

Consistent Light Primer Strikes

Light strikes with S&H sear in a 4-position burst pack

Kimber Micro 9- Weird Primer Strikes - Workbench - Full30

Light primer strikes??

Odd Primer Strikes

Bearcat light strikes?

Light primer strikes - AK-V - Palmetto State Armory

Light primer strikes on revolver - SASS Wire - SASS Wire Forum

7.62x39 light primer strikes

What caused this primer failure?