I had a crash of UE5.1 a few weeks ago and the error must exist since then.
Another user opened my project (everything exactly the same, with no different settings) and it was, unlike my file that was too dark, super bright and all the light sources worked. I’ve also install it on another device and again, it was bright.
So the only thing I had to do was to reinstall UE5.1 itself, verifying didn’t work. And now – everything works perfectly again. 