Huge problem with Light scenarios and sub levels

Hello there,

We have started a new portfolio project which will combine several projects into one, from where we can access all our projects via gameplay.

Each project has its own map.
For example Project 1, Project 2 and Project 3

Our Master level is Project 3 and we has aplied Project 1 and Project 2 as sub levels.
Project 3 (master level) is divided into sub levels also, for example Foliage, Light, Architecture, Accessoaries for optimization purposes.
So we can load and unload these levels when the player is not able to see them.

Project 1 and Project 2 are completely different levels ( each of them with totally different light setup, materials and functionality) so we decide to convert them to Lighting Scenarios.
Project 3 (MasterLevel) and all his sub levels doesn’t have Lighting scenarios.

No matter if we bake the light for each of them separately or for all of them at once we always end up with strangely lit scene, with the “Light need to be rebuild” warning and the “Preview” stamp on the materials.

When the player goes to Project 1 we unload all sublevels and load this particular one to make sure only one lighting scenario is enabled at time and there is no other sub levels loaded.
No matter from where I rebuild the light we end up with unbaked light.

I think if I create new Master level and then combine Project 3 ( previous master with sublevels ) into 1 level (so no sublevels at all), add Project 2 and Project 3, then make each of them a lighting scenario will work out. The flaw of this method is propably we wont be able to load/unload the foliage and arhitecture from Project 3 since they are already combined into one single level.

We already used the old “Open level” way, which I must say is a quite outdated way to switch between levels, especially since we already have the “Streaming level system”.
The trouble is that apperanlty does not work as intended or at least we are not able to get it to work properly.
If there is no other way we will be forced to switch back to the “Open level”, but that would mean the SLS cost us two weeks without any particular success.

Is there at least a way for us to change the steam loading screen (see the attachements), so while everything is frozen up or loading the player is not stuck seeing that?

Did you find a solution to this?
Our Lighting seems also not to work properly in packaged game.
Very similar setup with sublevels and lighting scenarios.