How to move large nubmer of meshes

Hello,
I am building a symmetrical multiplayer map. Half of the map currently has 20,000 plus objects.
When I try to copy and past that to the other side of the map the engine is extremely slow.
It takes 30 mins to make all the meshes move an inch. So trying to copy paste flip and line up is nearly impossible.

I have a really good computer and nothing is even close to maxing out so it seems to be an engine limitation issue of moving that many objects at once. Does anyone know of good workaround to copy one side of a level to the other that has a lot of objects?

You could stream in two copies of the same level. You can load instances of streamed levels at a given transform.

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