I suspect Desmos isn’t able to consistently grab the correct x’s and y’s from an aggregate, essentially pairing up sets of x’s and y’s that aren’t really pairs at all, but do come from somewhere in the aggregate function. Down to a timing issue or registering the aggregate function I believe, since I’ve seen aggregate delay times of upwards of 30 seconds in some instances.
I posted about this here a while back: Aggregation Plot Errors