Pistol Cases, not rifle
steelman762, I think you misunderstood. The O.P. has experience loading .223 Remington, but the question is about pistol cases. (The O.P. still has not told us what caliber, though.)
I look forward to his next post.
Yes, fouling in the primer pocket or primers not fully seated does cause misfires, hangfires and such. Usually a second strike will succeed.
Primers should be slightly BELOW flush when properly seated.