I am doing this work in 2.1.4
A bit stumped by this... Currently I have a level scene, that has segment scenes as children. Each segment has platform scenes.
There isn't much to the platforms scenes, they have a collider and some textures.
When I click on this scene it loads fast, but when switching away from it, or exiting, it stalls the editor for 2 minutes.
Initially I thought maybe it was tool scripts, but I cleared them all off. I remade the scene and it seemed to be working fine for a moment, but after re-opening it later, the problem continued.
It only alleviates when I reduce the number of platforms in a segment.
Is this an editor bug, or does anyone know of anything that may be behind it?