It’s as soon as I’m launching the game, I’m not spawning anything during runtime …
And besides, I have this problem only on some levels.
EDIT: It appears to be caused by lights (but I’m not sure…)
EDIT 2: After some checks, it appears to be caused by a spawned Spot Light (which was set at “Stationary”, and when I’ve changed it to “Movable”, no more problem …) Also, I had to set a Directional Light to Movable (even if this light is already in the level, and don’t move …)
Thank you for your answer 