(Updated)Thunderhorse starting to right itself, Investigation continues

BP still is not saying why it's Thunderhorse rig was taking on water but it would appear progress is being made.

Tom Fowler has apparently found someone involved with the salvage operations that is willing to talk (scroll down to the bottom).

There are of course rumors percolating through the industry about what happened and why. Some of the rumors/theories I've seen and/or heard:

Inspection ports in the hull and/or ballast inlet covers being left off that were unnoticed as long as the active ballast control system could keep up with the flooding, but when the system was shut-in during the evacuation, the pumps were turned off, allowing the flooding to continue unchecked.

Bad valves or valves inadvertently left open allowing ballast to slosh from one tank to another or to seep in from the surrounding ocean. Again, if a valve was leaking a little, the active ballast system would mask it for the most part as long as the system was active.

Design flaw with the active ballast system itself.

Anchor damage to the hull that was not found on the first ROV inspection.

My previous theory of a control resonance issue could not have been the case because the power system had been secured and shut down prior to evacuation, so the active ballast system could not have been operational, but check valves in the system might be leaky.

UPDATE:
BP has issued a status report press release that again emphasizes plugging ballast inlet and inspection ports..... Is this just a result of a lazy shipyard worker not putting the covers on before it was floated? Wouldn't THAT be a kick in the head.....