In the sense of just completely making up references out of nowhere? Very low. Humans make mistakes, of course, but they tend not to be so egregious. Grounding

In the sense of just completely making up references out of nowhere? Very low. Humans make mistakes, of course, but they tend not to be so egregious. Grounding a submission on a made up reference is quite likely to be fatal to your case in a way that most human errors aren't.