Hello, we are having the same issue. The medicals are booked up. It took three months to get an appt. The medical packet arrived late and the expiration date of the I797 has passed. I asked the US Embassy in Dublin if it can be extended and was told it's up to the Consular Official who oversees the interview.
Also, we sent out Readiness Notice last week. Now waiting to see if/when the interview is scheduled. It's a very stressful process! I wish you the best of luck!