Repro: Create a new project with e.g. first person template, make the base platform big to the horizon and with foliage tool paint (using big brush like 30k radius, ~200 density and 1.0 weight) many instances, to reach 200/300k+ instances. Then click PIE and it will crash. Even more, when I try to open the crashed project again, it crashes and can’t be opened anymore.
Here is the broken project if that will be useful. (Don’t mind the name, I was trying to reproduce another bug with instances…)