Hi guys, I´m creating a solutionfor a part that we already had in solids, so I cutted the solid with surfaces at some points, and created some surfaces

from the resulting edges, or created 0 offsets to "copy" others.  So I have the atacched surface, and when I try to thicken it to 1.7 mm inwards (or offset it the same amount ) that is whatI need;  I get a really strange thing, on both cases the preview shows what is supposed to, a yellowish surface 1.7mm away from the base one, but hitting enter, creates a strange solid (or offset surface) that has that 1.7mm on the top but down intersects itself.

I really don´t know why Solidworks do this kind of stuff, or may be is me, but if the preview shows exactly what we designers expect, why produces a completely different result afterwards?????

I really appreciate if somebody tell me what can I do.

Thank you in advance

Victor