UI Rendering Glitches After Spawning Multiple Entities

bevy_rapier version: https://github.com/indiv0/bevy_rapier/tree/5d19dc991cc3f18d9012524d08ff30ade915a2ae
bevy_webgl2 version: https://github.com/indiv0/bevy_webgl2/tree/a53c9ca296a46019d833da9be6f69f099ac63159
bevy version: https://github.com/bevyengine/bevy/tree/2e2423139e0cd8efda3aa0d474d3eb231dad566b
Example source: https://github.com/indiv0/colonize/tree/75ee66f710a4b9444a4b2119f27422e6fdeb3723
Example compilation args:
```
cargo build --target wasm32-unknown-unknown --no-default-features --features wasm
wasm-bindgen --out-dir target --target web target/wasm32-unknown-unknown/debug/colonize.wasm
wasm-opt --debuginfo -Oz target/colonize_bg.wasm -o target/colonize_bg_opt.wasm
sed -i 's/_bg\.wasm/_bg_opt\.wasm/g' target/colonize.js
```
Example demo: https://dev.colonize.rs/
rustc version: `rustc 1.50.0-nightly (f0f68778f 2020-12-09)`

Hello!

I have a game I'm working on. Currently you can spawn cubes in the game by pressing `T`.
This will attempt to spawn cubes in the air in some radius above the origin coordinate.

On some platforms (Firefox on Windows on my laptop) I've observed behaviour where if I spawn a lot of cubes at once
the UI begins to glitch out. It's not a framerate issue, but rather meshes start being drawn/not drawn at random.

You can see an example of the behaviour here:

I think this might be caused by me spawning rigid bodies/colliders within one another since my spawning algorithm doesn't prevent that, but what's weird is that it doesn't happen on any other device I've tested.