Tell me about a project that went significantly off track. What happened and what did you do?
Ownership and recovery methodology. Every experienced PM has a troubled project; candidates who claim otherwise read as junior or evasive. The panel wants to see whether you detected the slip early, what you changed, and whether you communicated it honestly.
Pick a project where the trouble was real and partly yours to catch. Cover how the slip was detected (ideally by your own tracking, not a stakeholder complaint), the recovery options you weighed (re-baseline, descope, add resources, phase the delivery), the one you chose and why, and where the project actually landed against the original baseline. End with the change you made to how you run projects since.