It's a raytheon ATFLIR[0]. The rotation precisely matches the point at which the 'up-down' tracking reaches it's upper stop and the body of the pod has to rotate. The concensus was that it's some internal reflection within the pod window.
What "consensus"? I've read the Wikipedia article on the incident and found no information of any consensus of this sort. The objects in question were visually tracked by multiple aircraft, and were detected by multiple radar systems.
[0] https://www.raytheon.com/capabilities/products/atflir