I was wondering if the recent seismic activity in the general area, may have caused the topography of the sea floor to change, making the charts obsolete.
It could have been a mechanical problem with the dive planes that caused the sub to hit the bottom.
"Jam dive" and "Jam rise" casualites are drilled continuously. Planes movement is also limited at higher speeds.
Whatever caused it, is certainly was no minor brush with the bottom. We may be fortunate that we didn't lose the entire crew.