This has got to be the strangest cause of lag ive seen yet lol.
I played it, saw how long it took to load and was like "wait wtf, this looks like maybe 3000 or so objects, why does it feel closer to 30 000?
Then i looked in the editor...
Yes, there is an excessive number of of props used...
But each building should only be like 20ish props...
So i looked....
And Dude...
On every building...
There is ONE window, often fully hidden, that had been duplicated 128 times (!!!) per building.
That is some spooky stuff man.

Noice