Bruce, I use Vluzacn's ZHLT compilers with just "-extra" setting. And I never had any lightmap artefacts with them like this. And a weird moment that there is a darken square on a wall that supposed to be white. One brush with simple texture.
Thanks, folks! I just realised how zhlt_copylight works and that is what I needed. I also tried changing origin, that worked too, but in comparison just waste of time. Again, thanks to everyone who tried to support!
Here is how it looks when I'm rying to make its collider with NULL-texture:
I like what shadow it casts, but I don't want it to affect the brightness of model. I've tried different ways and entities, but seems don't get how to make a proper shadow for the model.