Lighting goes weirder each time I'm loading a new scene

- We have a main menu scene with just UI & no lighting
- We load a scene with static meshes, cloths etc with both baked and realtime lights

On each run of the game we can switch between these two scenes quite a few times between games, each time the lighting seems like it "burns" the texturing more and more and goes darker in other places. In different graphics cards we see different results as for example on my computer I see the weird effect for some seconds but it looks like it's trying to fix it as it goes but when the camera in the lighted scene switches position or moves around lighting goes nuts again, on one of the team's pcs it just goes weirder and weirder each time he reloads the lighted scene ( both pcs have modern Nvidia cards, GTX980 & GTX760 )

Check the attached picture, top is bad, bottom is how it should be