Bug light, object randomly disappear

Hi,

I have a "bug" I t$$anonymous$$nk for a month now. I'm using Unity Labs and I delete the ObservationRoom to use my own room. But the objects/walls/ground randomly disappear when I'm moving. When I say disappear, it's just invisible for a second and then it's visible again (I can walk on it even if it's not visible). I delete everyt$$anonymous$$ng link to the observation room so there is not$$anonymous$$ng left where I create my room.

Can someone help me please ?