Permit to Work: where does yours break down in practice?

The system is rarely the problem. The breakdown is usually at a seam — an isolation certificate that references equipment by a tag number nobody uses on site, a permit issued for eight hours on a job that needs twelve, or a shift change where the permit is handed over but the hazard briefing is not. We are interested in the specific failure points, not the theory. Where does your permit to work system get worked around, and was the workaround a sign of a badly written permit or a badly planned job?