Regarding the issue of Child Actor
It looks like the materials are losing references. This would explain why changing RenderMode fixes it (sometimes), as that will force the PC to recreate and redistribute new materials.
I’m guessing it’s because building it via Child Actor doesn’t link those references automatically.
Good news is 0.5 is immune to this 
Bad news is, 0.4 isn’t 
Regarding Packaging
I haven’t tested streaming levels and currently have no idea how that affects things.
At first glance it looks like there is a problem with PC issuing a rebuild broadcast to the actors, as they cannot register new components. My best guess is the PC tries to rebuild itself before the actor’s world is actually initialized.
Try placing a world guard in the APointCloudActor::RebuildComponents:
replace
if (PointCloud && !PointCloud->IsDirty())
with
if (PointCloud && !PointCloud->IsDirty() && GetWorld())