Not posted here before and have limited experience with Simplify3D as have been mainly using Cura.
I have modelled a part in Inventor and then exported as an STL, I loaded into Simplify3D and all appeared fine, until I processed the part and noticed a strange error on layer 23. Basically there is an internal thread and for some reason on layer 23 an outside layer is placed acros the entire internal thread, layer 22 and 24 are fine. The images show this error and tried playing around with a few settings but unsure what is causing it, I have not printed internal threads on Simplify3D before until now.
Simplify3D solid preview appears fine

Simplify3D Layer 22 then 23 and then 24



Cura layer view and original Inventor image


I then looked at the part in Cura and this is fine, making a test print from Cura now, image attached as well as a photo of the original drawing from Inventor.
This is Simplify3D version 3.0.0
Any ideas would be greatly appreciated
Suze