The knocking you feel in the EPAS is somewhat common on both 2011 and 2012 models, and it is also in my truck. It started doing that around 2,000 miles on it (currently 9,000). The problem is poor QA at assembly and changing vendors with QA problems there as well. AFAIK, there is no real fix for it.

Guesses for the problem are: Electrical, mechanical, or both. On my truck and many others the sensation comes and goes. Typically, when it is knocking (usually felt and not heard), the steering can also be overly sensitive; and it will often stay in an over boosted mode at highway speeds. There will be other times it will tighten up and actually stop the knocking and stop the over boosting. Also when my truck is in the over boosted and knocking state the wind correction does not work; when the steering tightens up like it should the wind correction technology works great in even 40-50 MPH cross winds. All this leads one to believe much of the problem is electrical and the computers electrical control of the mechanical steering parts.

AFAIK, with all those reporting this same problem; Ford still does not seem able to address the problem, nor even understands it.