There are redundant systems in place that handle the fly-by-wire systems. Keep in mind that these systems are gliding a brick in. Systems computer controlled but the pilots are capable of doing many things manually. And the pilot does land the vehicle manually. But if the code was modified such that it suddenly turned the shuttle during re-entry? You can assume that NASA has the systems code locked down. Or can you?
See here for a basic primer on the shuttle system.
As far as some damage to the wing? If the wing was damaged enough to allow burn-thru and then the wing failed that might explain the sudden change in the glider's direction. The wing is breached then is sheared off then....
Many of these questions will be answered not by the video we have been seeing this morning but by the video NASA was taking from various sources as they usually do as a matter of course.