»» What about if you go and look at it from the other side, can you see it on the other side or is missing from both sides?
Yup, the poly is missing in the booth side.


Ok I have replace moi_lib.dll with the original one, and restore the .ini. (sorry you reply too fast :))

The problem is still there ... there are 72 overlapping vertex in the object. After the 0 radius merging, and a double flip, only one triangle if still missing.
Looks like the model generate a lot of small radius overlapping vertex. (an other merge with 0.1 mm radius remove an other 138 vertices :S)