Hello Everyone,
I’m currently working on a 4.18.1 project, and since some days, even when I’m applying lighting build, I have still the error message “Lighting needs to be rebuild”, but only when I launch the game … 
Can anyone help me about this ?
Thank you in advance for your answer 
when it is only when launching the game then you are spawning static Meshes which are set to static.
Meshes which are spawned during runtime need to be set as Moveable.
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