[Yo-Yo]

Or interaction between the onboard gyro torsion field and the Earth's (or other planet's) torsion field.

From the article:

The five other flybys involved flights whose incoming and outgoing trajectories were asymmetrical with each other in terms of their orientation with Earth's equator, which "suggests that the anomaly is related to Earth's rotation," Anderson told the Times Online. As to whether these new anomalies are linked with the Pioneer anomaly, "I would be very surprised if we have discovered two independent spacecraft anomalies," Anderson told SPACE.com. "I suspect they are connected, but I really do not know."

[Jack Hydrazine]

Is it me or do these astrophysicists sound as dumb as a box of rocks? I guess they never received the memo on torsion fields or how the rotating bodies like planets and gyros might interact with one another.