Hi guys, I'm currently working on a dynamic city system, which moves buildings around and active/deactive them base on their visibility. When I was using 5.6.0, it's all great, I can run a 6km * 6km size city inside editor at 200FPS. But I cant remember when(most likely 5.6.1P4), things got changed. Editor freeze for a little frame whenever a building is active(however the fps showed in stats of game view never drops..), and this is editor only, everything is good in a build player. I admit that the each one of these building prefabs contains tons of gameobjects, which is bad and needs to optimized. But I cant understand why this happen only after 5.6.2 and its getting even worse in Unity 2017. I've read some post about unity is optimizing its transform system, could it be possible that the new transform system(or hierarchy view?) inside editor have problem of handling complex transforms? The project is to big to upload for a bug report. Is there anyone who had the same issue or solutions.? In the attached files, 1.png shows the hierarchy of one building prefab. 2.png shows how the viewculling is working. It's actually not much alive buildings at one time. 3.png shows the fps inside editor. however, it's incorrect...because when ever a new building is active, it freeze..