You "did" cover the third thing. I just didn't read far enough to get the detail.

Most folks jump right to "bad primer" or weak firing pin spring and never consider a brass problem.
If you say "this is the problem" you better be able to back it up before blaming one thing.
The firing pin spring is weak.
The primers are bad.
Be able to prove what you think is the problem. Don't just throw $$ at it.
Looks like you pretty much covered it.