These are scary thoughts and I hope we never get to that point! Can you imagine the tangled web of blame and liability to fight over?! (Was it measured correctly but improperly laid out, etc etc).
A course I certified was found to be wrong (a half marathon in Williamsburg, VA). The mistake came because of a calibration course that was certified at the wrong distance. I had failed to catch a math error on the part of the measurer in computing the cal course length, so that error just propagated itself to any course that was measured using the cal course.
To resolve this one, I went down to measure and certify the course at no cost to the race. That worked ok. I'm glad nobody sued.
The Williamsburg course was too long, hence the complaints. Fair enough. Another course I had measured myself, a 5K in Maryland, turned out to be way short. In trying to be "efficient" by measuring this 5K at the same time as a 10K, I just messed up the numbers. But the runners had just reported that the mile points were off-- they thought it was the right distance overall! (How we do like to believe we are faster than we are!!) Again I resolved this one by just doing another certification with no charge to the event. They were fine with that.