It is possible that I did not drink enough fluids the day before or that morning. Maybe I was dehydrated and it caused hyper-sensitivity.
I actually purged loose stools at night around the time of drinking the olive oil, but it settled down and I slept well. I probably should have drank a bunch of water at that time to replenish the fluid.
The first time this happened (3rd flush) the only thing I had eaten just before the reaction was some almonds. Knowing that a lot of people are sensitive to nuts, I figured that must have been it. But this time I had a reaction after just some relatively benign foods that I eat all the time.