It seems that depending on the number of actors and/or lights, shadows and lighting are completely destroyed in UE5.2:
When removing some actors or lights, it works as expected:
This didn’t happen in previous Unreal versions.
You can check this example-bug project from here: Dropbox - BUG-Lumen_shadows_dissapear.zip - Simplify your life
PS: I’m not going to report it through the Bug Submission Form, as I’m tired of being ignored.
Apparently the engine update has brought new bugs, Disabling raytracing in shadows solves the problem. But it’s better to stay on 5.1 I thought at first it was only in viewport, but in the renderer with shadows is a nightmare
Hey folks, our team is trying to reproduce the issue with little success—they recreated your scene in 5.1.1, then opened in 5.2 via Open a Copy.
Could you share more specific details about your steps to 5.2 that may help them track down the problem?
Hi @Amanda.Schade ,
I cannot identify the certain steps. I will continue trying it tomorrow, but I have recreated this 5.0 scene just copying the cubes and the lights in the already provided 5.2 scene:
5.0:
5.2:
You will be able to open it normally in 5.0 and 5.1, but it will show destroyed lighting in 5.2. (Notice in the World Outliner an InstancedFoliageActor when opening with 5.2, which was not added in the 5.0 scene).
I noticed this same lighting issues when I opened some of my older projects, that’s why I tried to isolate the problem and report it, and provide a proof-ready-project.
Nothing special done, but also not sure when or why it happens.
Hi @Amanda.Schade ,
I have continued doing tests and I have noticed a certain scenario (may be more, as there are tons of combinations).
For a 100% success scenario, it seems related with any project created with a different version than 5.1 (As I couldn’t reproduce it creating the project with 5.1 version). I have recorded this with a 5.0 project, but if I noticed this error before, it’s because I also tested older projects, made with UE4.27 for example:
(If created with 5.0, but opened later with 5.1 and saving the changes, to ‘convert’ the project to 5.1, the error will persist anyway. This is also shown in the recorded video)
Steps summary:
Perhaps it may be related with other raytracing shadows bugs, if something is broken from ‘the base’. Despite of the tittle of the post, these are bugs 100%. The question was rhetoric:
Thanks!
Thank you for the detailed steps! Our team was able to reproduce the issue and logged the issue for our dev team. It’s been added to the tracker here: Unreal Engine Issues and Bug Tracker (UE-185922)
Thank you @Amanda.Schade , I see it! 
EDIT: Oh! I have found a much more easier way to reproduce the issue, and native in 5.2! Hope it helps:
Please! If you could slightly look at those other ray-tracing-shadows related bugs, I would be very happy. Super easy to reproduce the steps, if you have interest. 5-10 minutes testing.
And please, (please!) moving assets (in the correct way, of course) inside Unreal is broken since many versions ago. How’s possible? A so elemental and must-have feature 
. Super Easy to reproduce too, just following the video provided and the provided project too. 1 minute testing:
Thaaaaank you very much!
For the original issue here, it’ll be fixed in the next release.
In the meantime, you can switch to SM6 to solve the problem—go to Project Settings → Platforms → Windows → D3D12 Targeted Shader Format → SM6) or run with -sm6 on your commandline.
Hope that helps!
