What does DRC still fail to catch in real-world PCB design?

I’m researching how PCB designers actually review boards before sending them to manufacturing, and I’d love to hear from engineers with real-world experience.

I’m not selling anything—I’m trying to understand where today’s workflow still falls short.

A few questions:

1. What’s the last PCB issue that made it through DRC but was later caught by a senior engineer, during design review, or after the first prototype?
2. What’s the most expensive or frustrating PCB mistake you’ve personally experienced?
3. If you could automate one part of the PCB design review process, what would it be?
4. Do you feel current DRC tools are enough, or are there things they simply can’t catch?
5. Before releasing a board to manufacturing, what gives you the most confidence that it’s actually ready?

I’d really appreciate detailed answers rather than simple yes/no responses. Real examples are especially valuable.

Thanks in advance!