It keeps lagging EPICALLY when I load a project

It’s crashed my Mac twice now. No one can say it’s the computer, this thing is brand new, desktop, i7, etc. When I start, it’s fine, great even, but if I save it, and close out, then try to load the project, everything goes to hell, and it’s extremely laggy, then the whole computer crashes. How do I fix this? It does the same if I package the game and try to play it. Completely unresponsive. Also, it says something about fixing the lighting, and 18 unbuilt objects, what’s that mean? I deleted the lighting because I didn’t want it, why would I rebuild it?

iMac (21.5-inch, Late 2015)
2.8 GHz Intel Core i5
8 GB 1867 MHz DDR3
Intel Iris Pro Graphics 6200 1536 MB

It probably is the computer. I’m not saying the desktop has issues, macs just aren’t strong enough for UE4 development. It’s not at all the platform you want to use for anything game related.

It lags some time , but you have to upgrade your pc

Lagging is normal issue.This will keep surfacing until you change your machine.

I had the same issue and let me tell you lagging can happen anytime, Try to replace your machine with a new one, this might work for you.

I was facing the same problem. what is the solution of it.

I think you have to upgrade or change your machine.