This was caused by a cheating player who has since been banned. I’ve reported what happened to the dev team so they can look into how this affected the player’s score and so they can fix up the Guild’s score to what it should be without the cheating players’ involvement.
I would just like to say that just because one player in a Guild is cheating doesn’t mean that anyone else in the guild is a cheater or condones this behaviour. It can be difficult to know when someone in your own guild is cheating, in this case they cheated so hard it looked like a bug, so it was easier to spot.
So please don’t hold it against this person’s Guild mates, 99% of the time the rest of the guild has no idea it’s being done and don’t condone it or want it in their guild.