Shadow Value Problem

Hi,

I’m working on my first archviz project and got a problem with one of my mesh. It has different shadow values in places where they should be the same, what couses strange contacts shadows between shelves and a wall behind them.
I’ve created the mesh in blender, I’ve also unwraped second texture channel for lightmap. Engine Scalability Settings are set to epic and Light Quality is set to production. What I’ve tried so far:

  1. high resolution lightmaps (2048),
  2. disabling AO,
  3. high lightmass settings (screenshot)
  4. I put an addidional spot light which was pointed directly on the mesh, but after baking, the contrast between them was still visible.

I’ll really appreciate your help.
Some screenshots: