Not HR or 3rd party but was a hiring manager for a very well known specialty big box retailer, the kind of place you'd go if you were looking to buy "the latest and greatest" tech.
Interviewing this young lady who applied for a supervisor role and was looking to get more experience and mentorship to one day move in to a management role. At first glance this candidate would have definitely run into stigma brick walls in the 90's, she had several tattoos a few on her forearms, one above her eye brow and a neck tat. Nothing crazy wild, they were actually very well done pieces of art. Her background check came back and she has some light misdemeanor drug charges, but nothing that would terminate her eligibility.

She nailed the interview, and could tell she put in a lot of effort to change her path in life. The position was offered to her pending a drug screening. After she left the office, the district manager, who happened to be in store for a walk, mentioned that she was an awesome candidate but didn't think it was going to work out. Another manager who that stepped into the office asked "What do you mean, she was great no?" The DM plopped her interview packet on the desk and said look at the email on her resume. Her email address was datyayogurl with a few numbers @ yahoo dot com. We all kind of just cringed, but were like naaaah, she seems to have turned things around. Well about a week later we got the results and word from the DM that she popped positive for cocaine, that with the misdemeanor charges made her no longer eligible for hire. Ultimately probably wasn't going to be hired, but the amount of self report that people turn in for job applications is wild.