Inconsistent clustering when entities are at similar positions

I have been noticing some pretty weird and inconsistent clustering results lately. Here's one such example. I placed 2 entities very closely together (~500m real world distance) and assigned them billboards. Afterwards, I pan the map along the y-axis. Since the entities are not clustered in the first frame, I wouldn't expect them to be clustered in the last frame, given the coordinates are the same.


Can somebody tell me what's going on? How do we fix this?

Start by reproducing the clustering behavior shown in the linked GIF: place two entities about 500 m apart, assign billboards, and pan the map along the y-axis. Investigate why clustering changes between frames despite unchanged coordinates; done means the clustering result remains consistent during the pan.

Written by the indexing model from the issue text.