I have loaded since the 70's and have yet to have a major mistake.
I always check the inside of each case for materials inside and the cal. on the head stamp before putting it with the other cases.

Then I can clean, tumble or what ever when I get time to start
my loading process, either part way or to a completed loading.

Making sure you start off with the correct and proper materials without flaws is #1.

Take your time and do a good job.