hi Viktor .. can you check this please :

also fails @ rendering

This is polygon with 16 holes.
It is valid polygon.

Problem is with LightWave triangulation. They are using several different triangulation methods.
The worst one is that real-time version, used for OpenGL drawing of complex polygons.

You just need to switch to NURBS. In this case LWCAD is triangulating.
And for rendering, FREEZE nurbs and triple complex polygons with issues.

I will probably redo this, so each frame line will be separate polygon, instead on single complex polygon with multiple holes.
But not in this version.