Hey,
Things were all good in the first two levels (the ants are in level 2)of my VR experience for the Quest. But when I hit level three, performance went south – and it stayed that way, no matter where I went.
I played detective this morning and cracked the case. The problem was the blueprint that spawns the ants, who follow a set path along a spline. This blueprint lived in the second level’s streaming world, coming and going with it.
Now, here’s where it gets interesting: In the second level, everything was A-OK. Ants spawned and got destroyed when they reached the end of their journey on the spline. No problems there. But when I left that level, the ants that hadn’t reached the end of the spline hung around, never getting destroyed causing trouble when I returned, and even if not, they stay there.
And it wasn’t just about the number of ants. I tried optimizing them, making them 2D instead of 3D, randomizing spawn times, and simplifying or removing animations – but the issue stuck around. With 1 or 100 ants, exact same result.
So, my solution for now is saying goodbye to the ants. I don’t have the time to dive deep into fixing this at the moment, so I removed the ant system. 
The result? Smooth experience, capped at 90 FPS. 
If I ever revisit this issue, I’ll be sure to share how I fixed it.
Thanks for your time @VictorLerp