A very thin possibility. Is it that unbelievable though that shooting with a tripod and 800 speed film in a brightly lit church would produce such a result? Or perhaps the people standing blocked a lot of the flourescent light that was causing the problem in the other shots?
I did get a few other shots to come out that well, all without the flash.
I don't think a flash was used. If you look at the shadows, they are the same. I would say that the exposure changed for whatever reason, for example more sunlight through the windows, and when the scanner on the printer saw the negative that is how it was printed. It is not unusual for that to happen. I think if you had a pro lab print them you would have had better results, even from machine prints.