nothing is fool-proof...what is a comprehensive back-ground check?

A side note...when I was in the Army I knew quite a number of people that accepted a Dishonorable Discharge just to go home...most of them were drug related. But instead of taking the Army's punishment they opted for a dishonorable. They were like me, between 19 & 22, but they had no clue
of the life-long ramifications of a dishonorable discharge...Sad.

This is from 2015

https://www.thetrace.org/2015/07/gun-background-check-nics-guide/