An old one I know - but for me the problem was, that in the c++ file where I spawn the projectile the FActorSpawnParameters had the flag bDeferConstruction enabled - this causes that the construction script is not executed and therefore the projectile was not properly initialized. So I had something like:
FActorSpawnParameters SpawnParams;
SpawnParams.bDeferConstruction = true;
SpawnParams.Owner = GetOwner();
SpawnParams.Instigator = GetOwner()->GetInstigator();
SpawnedRef = (ASuakeBaseProjectile*) GetWorld()->SpawnActor<ASuakeBaseProjectile>(ProjectileClass, CameraLoc, CameraRot, SpawnParams);
...
The solution for me was to remove:
SpawnParams.bDeferConstruction = true;
You can also try to set it to false, but that should be the default anyway… give it a try …
Cheerz … and happy Coding 
DaVe JeTedonner