Discussion I NEED HELP WITH LIGHTMAPS AND IMPORTED OBJECTS

I am getting completely crazy with lightmaps and .fbx objets imported to the scene.

I modelled a 3D object in Autodesk Fusion 360 which is a room where the avatar is going to walk through and whatever, it has like 18 objects in total. I exported from Fusion 360 to a .fbx file. Then, I imported that fbx into blender and I made the UV lightmap packs of every body like this.



I exported the resulting object and its lightmaps to another .fbx, which I imported into unity.

In Unity I imported the .fbx and I generated the Lightmap UVs (I think that step was not necessary since I already did it in Blender but I tried also the other way and it was also S***), I applied the right materials to all the bodies and generated the lightmaps. The settings are:



The quality was S***, a lot of artifacts, so I mannually changed the lightmap compression to High Quality for all the lightmaps:


After changing the Compression to High Quality nothing changed, this is what I obtanied:




And when I play the scene looks completely horrible,



I have spent so many many many hours in this, it is exhausting, sorry if this has been explained in other page but I have not found anything, I have tried all.

 

Thanks for the reply, how can I do that? after importing it to unity I create two UV maps in Blender for each of the bodies, the first one is a lightmap pack UV and the second one the object UV, getting also a very bad result... I also checked the troubleshooting guide and I could not fix the problem.
I know this is a complex object but I have other simple objects with awful awful results, like this:


The second one is a simple cylinder
This is the lighmap of a completely flat wall:

There is a lot of weird things in the middle like random wrinkles and lumps.


This is the shaded view of a flat wall with a lot of random lumps:

 

No, Generate Lightmpat UVs in the Mesh importer is unchecked. Models were created in Fusion 360 of Autodesk, exported in FBX, can be this causing the problem? Why I have this result? The material applied to the walls and floor is a simple white material made in unity