Streaming levels causes hiccups & brief stutters, how to avoid them?

I’ve been using world composition to stream my terrains / levels together to make a big world,
the problem is when in game and the player gets close to the next map so it streams in, the whole game pauses for a moment, and its not smooth at all.

I tried deleting a bunch of things I have in each map, but the problem is still there if I have more than just a landscape streaming in. Is streaming with world composition not really useful for piecing together maps that have stuff in them, and it should only be used for landscapes ?

Should I be loading all my static mesh’s and everything into the main persistent level and just culling them out with volumes instead?

Problem/Question persists with 4.18