I was charged 10,000 for rabies shots administered in the ER despite calling and getting pre-authed. Their billing dept fat-fingered my insurance companies address. Yes, that was the unique identifier - a physical address. I had to fix it myself.

Unrelated but I was also audited a similar amount due to clerical error by robinhood + irs. Unnecessarily complicated laws designed to screw 99% of us are working.