Background checks are often horribly wrong or contain bullshit red flags like, "Claimed position: Developer; Actual position: Architect". Get enough of those and you'll be dropped for consideration.
When I left an employer a few years ago I requested my employee record and what was inside blew my mind. The background check was so wrong it was crazy. It said I worked at places I never worked. It said I lied about my work history (aforementioned title naming problem). It said my provided address information did not exist!
Fortunately none of that seemed to matter to the company that hired me but I suspect it's only because the supposed red flags were ultimately meaningless (did I work as a customer service rep at some company 8 years ago? No. Was it relevant? No).