It seems that as a result of the way we have our cache structured, we are not properly removing players from their respective groups' cached loot data when they are removed from the group.
This relates to the way we store data in Redis, and the fact that the keys we delete on each 24-hour invalidation only include player-specific keys, not those that are involved in z-scores; which is where loot totals are extrapolated from.
This relates to the way we store data in Redis, and the fact that the keys we delete on each 24-hour invalidation only include player-specific keys, not those that are involved in z-scores; which is where loot totals are extrapolated from.