Oops...

After a good night's sleep, I don't need a rocket scientist to tell me my hypothesis to explain the mismatch between real life and what the computers predicted was a (bad) shot in the dark. Mating two masses that are in orbit will not cause the orbit to change, since to assume the opposite implies that the act of docking causes a force to be exerted, which in turn would change the orbit.

Whatever the cause of the discrepancy, it's something else.

Cheers...