When I use to monitor the temperatures during cooking more closely, I often noticed a "minor" stall around 140°F. I did try to find out what causes this. What I learned is at 140°F temperature that is when proteins denature (change shape), and during that process release moisture a lot of moisture. This release of moisture causes that minor stall. The length of time these "minor" stalls last would depend on the mass of meat. One hour would be within that range.
It is best to finish the turkey in the oven anyway to crisp up the skin. How big was your turkey?