But, the radar kept showing collision bearing
and descending altitude, still about 4,500 feet.
Just about any Intercept 101 course would define this as perfect collision bearing. Throw in the fact that the Link altitude of this track was exactly the same as mine, and you have a situation warranting further examination.
We learned later that the Eagle pilot had lost sight of his formation, and was attempting to rendezvous with us (hence the collision bearing).