Aggregation generating different data

Interesting situation.

I have aggregation generating a set of points that is displayed in a graph. However the generated set of points is not the same for every student. See here for a sample of what students saw:

What might be the reason for this? I have a suspicion but thought i’d throw it up here first to see what others thought.

Reduced test case here: aggregation • Activity Builder by Desmos Classroom

This seems to be an important bug for anyone doing aggregation so I’ll move this to the Bugs section if there are no ideas in the next day or so.