4.17.1 Building Lightning never end

Development Rendering
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Hello everyone,

I’m facing a really specific bug that was really difficult to spot correctly.
The static lightning building never end and stay at 90%+
In the swarm agent log, all seems working fine, the baking goes really fast to 100% and that’s all.
Well, to reproduce this bug :

  1. Create an empty project on U4.17 (You can add the StarterContent we gonna need a static mesh later)
  2. Add a new C++ Class “UMyPointLightComponent” that inherit from “UPointLightComponent”, do not change anything at the generated code.
  3. Create a new C++ Class “AMyActor” that inherit from AActor this time and add your “UMyPointLightComponent” as a child of this new actor.

In other words, add this to your “MyActor.h” :

UPROPERTY( meta = ( DisplayName = "Light" ), EditAnywhere, Category = "Light" )
UMyPointLightComponent *  pointLight;

And change your constructor in “MyActor.cpp” to this :

AMyActor::AMyActor() : 
	pointLight( CreateDefaultSubobject<UMyPointLightComponent>( TEXT( "Light.001" ) ) )
{
}

  1. Compile and create an Actor Blueprint and add your freshly created Class “AMyActor” in your Blueprint.

  2. Put everything with Mobility “Stationary” (including the “UMyPointLightComponent” child) and save your blueprint.

  3. Add at least two instances of your blueprint in your scene

  4. Add a static mesh ( the cube from the starter content will do the trick ) and put its Mobility to “Static” (for having at least one shadow to be baked)

  5. Try “Build Lightning”…it should stuck at ~90%

Well, it’s a really specific problem and any change in this work flow will not bug. (like changing the mobility to something else, instancing the C++ class directly in the scene…)
If I’m doing something wrong, I apologize and any help is welcome, because I lost many time and I’m actually stuck in my project.

Thank you in advance.