Howdy
As already discussed, the slight reduction of cylinder motion caused by a firing pin trapped in the dent of a fired primer will have no affect on lockup because the bullet will be long gone before the primer has been fully dented.
I do suggest you stop using fired primers as snap caps and instead invest in some actual snap caps.
The purpose of a snap cap is to gently cushion the impact of the firing pin as it comes to rest.
When the hammer slams into the frame as it comes to rest against the frame, the forces of deceleration are astronomical. I worked in the defense industry for many years, and we had instrumentation that could simulate the affects of deceleration, literally what happens when something comes to a sudden stop, for instance falling onto a concrete floor. Acceleration and deceleration are expressed as multiples of the force of gravity. Written as G. You have probably read that when a rocket is launched into orbit astronauts experience about 3Gs, or 3 times the force of gravity. Jet fighter pilots can experience 9 Gs before they pass out from lack of blood to the brain, that is why they typically wear G suits that put pressure on their legs to keep blood from pooling in their legs.
When a hammer slams into the frame of a firearm, the G forces approach infinity. Not 10 Gs, not 100 Gs, it approaches infinity.
With firearms with long thin firing pins, like the firing pin of a S&W revolver, when the hammer comes to a sudden stop against the frame, the tip of the firing pin wants to keep right on going. It does not happen often, but I have seen the tip of such a firing pin snap right off because of the G forces exerted on the narrow cross section of the firing pin.
When using spent primers as snap caps, after a few impacts the primer has been permanently deformed. It can no longer cushion the firing pin because it has taken on the shape of the firing pin at rest. The result is that without the cushioning affect, the tip of the firing pin will want to keep right on going when the hammer comes to a sudden stop.
Snap caps are specifically designed to cushion the firing pin as it comes to rest. Some use a spring, some use a resilient plastic. Snap caps can be home made by removing the primer from the primer pocket and filling it with a resilient substance. Hard rubber erasers, the type used for ink erasers can be used. Regular pencil eraser rubber is too soft. Some folks fill a primer pocket with silicone rubber, but I do not recommend that, silicone rubber is too soft will give way too much when a firing pin strikes it.
I recommend the snap caps made by A-Zoom. The purple ones. I use them in my firearms when I need to drop a hammer.
https://www.lymanproducts.com/brands/a-zoom