Shadows disappearing when building lighting

Whenever I build lighting the shadows disappear or turn into some glitchy scribble on the floor, the objects themselves also get very dark and the textures mess up, any idea why?
They look good before the lighting build however, as you can see here:

Thanks for any help.

The previous shadow was dynamic (temporary in your case). Once built/baked, if you don’t have good lightmaps, you don’t get good shadows, or in your case, no shadows at all!

If you terrain is a single mesh… it’s not gonna work with just 1 lightmap, even if it’s resolution is high.
If you use unreal landscape, you can increase it’s resolution in the landscape details panel.

One of the issues i had with lighting was the engine scalability for shadow was set to pretty low. See if getting the shadow to “epic” helps.