wirlybird wrote: ↑Thu Jun 21, 2018 7:58 amTry going to the Mesh menu and selecting "separate connected surfaces" and see if that helps.
This has fixed issues I've had with multiple files containing errors in the design that just happen to look OK in most viewers. There are many, many such files on Thingiverse. You won't see any changes in the layout view, but once you slice it, you will see the differences. One caveat: make sure the model is where you want it on the bed before using "separate connected surfaces" because S3D may actually lay out multiple overlaid pieces that are independent as far as moving, rotating, and scaling are concerned.