General Guidance:
Open-ended questions are best. They will disturb the current inertia because they elicit a thought deeper than yes or no.
A little humility doesn’t hurt. Begin the interruption with a statement about what you are experiencing. No one can argue with that. Even if you’re dealing with someone who needs to feel smart, they get a boost by the opportunity to provide an answer.
Check out this list for ideas.
Process Improvement Facilitation 