How to fix this lighting issue

Except for the floor, these meshes have the same material but they are visualised in completely different brightnesses while my goal is to achieve one organic wall/ceiling surface. How can I fix this with a moderate set of skills (it’s my second UE project) and a time budget of up to 15 hours (though I wouldn’t complain about a solution way faster than that).

The mesh is mostly skeletal and was created by 3ds max with morpher modifyer. A directional light is shining in, additionally I placed a point light in the room, there is no light importance volume yet.
It’s supposed to become an architectural walkthrough with many elements of the appartment shifting - should look good, of course, but doesn’t have to become a masterpiece.

I would be really grateful for your support!

I solved it by adjusting the directional light.

Hi, I’m wondering what are you adjustig in the direcional light ?

Hi, it’s a long time ago so I cannot say precisely any more what exactly I did. In general, I practically erased the directional light and had a shadowless diffuse lighting…looked like ■■■■ but deadline was approaching. I think in general the failure was based on the fact that it’s a dynamic object with dynamic lightmapping which the computer couldn’t cope with any more in terms of computing power at some point.