Bug? LightComponent does not react to variable changes with ProjectileMovement

So, problem is this: I have a flare grenade that uses the ProjectileMovementComponent, it has a light to light up the surroundings, but that should only turn on when the grenade “activated” and not when it spawned.
So in the Constructor, after creating the light I set LightSource->bAffectsWorld = false;
Now after I activate the grenade I set LightSource->bAffectsWorld = true;
The problem is that nothing happens, the light is still turned off, but the weirdest part is: If I eject from my Pawn, select the grenade and then either move it or change any variable, the light suddenly turns on…
If it helps, I’m on Linux (Manjaro, 4.4.5, KDE) and UE4.10.4