Weird crash when spawning many primitives

As part of a test scene, I’m spawning a bunch of primitive spheres (500+) and the editor crashes. This ONLY happens in my test scene (which contains a number of UI scripts along with it) - a blank scene with only the sphere-generator can spawn thousands of them without issue. Similarly, my UI testing script can spawn thousands of UI elements without issue. It’s only when I try to spawn sphere in the same scene as the UI that I’m limited to a few hundred spheres. I’m having trouble finding the pattern - any thoughts?

Pastebin containing the crash report