I filed in June 2017 in Brooklyn and this happened to me. I received an update on the app on September 26th, saying "interview canceled". I called USCIS a few times, and no one was able to give me a satisfactory explanation. Then, on October 10th, my status went back to "case is ready to be scheduled for an interview".
I called USCIS again a couple of weeks after this, and they advised that this was happening quite often around the country. Again, no real explanation as to why this was happening. They told me that all I can do is wait.
I hope this helps. My advice is not to worry about it, and your status should go back to normal soon. Fingers crossed.
I had the same "longer than expected message" on my account once the countdown reached 1 day.... in my case my status changed to interview scheduled after about 10 days on 7/25/18.
My PD is 11/2018 so you might be scheduled for interview soon.
