Hi Phiro,

re:
> This object have been made using boolean/intersection before extrusion.
> I think it's the source of this probem.

This is some kind of bug in the surface solver where the solver is not stopping at the trim boundaries of a trimmed surface like it is supposed to.

I've added this to my list of things to investigate but it is a difficult area to work on and so it probably won't happen until after v4.

Thanks, - Michael