Here's a small failure mode that costs real weeks.
DUring early design phase, a change comes through. Someone updates the affected requirement in the checklist — diligent, correct. What doesn't get updated is the evidence link underneath it, because that lives in a different file that nobody opened that day.
Months later, at review, the status says "compliant". SInce it is a review you open the evidence to look at it and discover that it describes the old configuration. Now you're reconstructing history under a deadline.
Nobody was careless. The traceability just wasn't holding itself together — a person was holding it together, and people miss one.
What's the worst "we missed one" you're willing to admit to?