Disapearing / Reapearing objects while moving in the scene

Hello i’m running into a problem i don’t know how to solve. When I’m moving in my scene objects will disappear and reappear randomly.
I have no idea why.
It doesn’t seems distance based problem because they could disappear either when i’m close or far.

I’m starting to have a lot of objects in my map (objects that are coming from a pack architecture from the market place) and because they have not being created directly in the project and just added i have log messages saying that i have external source references.
(which doesn’t sound like a problem but more like a fact since i can see my object, when they appear of course).

I have no idea if it’s related or not but hadn’t this problem yesterday but i have the problem since opening the map this morning

I’m using Unreal 4.8.3

Please help! Thanks :slight_smile: