Why are objects from other maps, suddenly coming into the current map when I play?

Right now, I am creating some game assets with Unreal Engine, making a few different maps (with different assets in each map).

Now when I press play in most of the different maps, everything seems to be fine. But in the one exception, I press play, and suddenly all the assets from every other environment (including the default maps), spawn out of nowhere within this single map.

what makes it even more bizarre, is that when I stop the level, all those assets seem to just disappear?

Has anybody else ever had a problem like this before?

Have you set up level streaming by any chance?..

I don’t recall turning it on, but I will check to see if that is the source.

Thanks

I don’t recall turning it on, but I will check to see if that is the source.

Thanks

It’s not that then, you’d know if you’d turned it on.

EDIT: Not sure. I’d probably need some more relevant info…