Who hired the structual engineer who found the defects? Was it the Board?
If so, and the Board was on notice of all these defects, it sounds rather suspect that someone would be brought in from the town to contradict the engineer. Who invited the town inspector to the Board meeting? And if there was any doubt, it would seem that further inspections by an impartial structural engineering firm ASAP would have been warranted.
It is possible that the sink hole caused this, and it would have happened even had the repair been made, but why take a chance with peoples lives?
Do the math.