Pulled and reseated the boards three times, and then power cycled the Corner Two satellite rack but the bump did not go away.  So I did some corner swapping, fortunately,  corner 2 and 3 are very close to one another and this was easy.  Very clear with this that the probe was the problem, unless it is the 1 meter long chamber to chassis in-air cable.  Thankfully, the CPS aren't contributing too much to the isolation at 80Hz.  Given that it is both CPS sensors on the Stage2 corner 2, maybe another snesor nearby on the platform is the problem.  I propose to power down other sensors on the platform to see if this CPS bump goes away--if that is, I've got nothing better to do.

For now we'll live with it--FRS 7576