Model is fine before slicing, parts are added during slicing process

[mjdpndbl]

When slicing my model, 3d printer OS is adding parts that don’t exist, making my print unusable.

I’m trying to make lens holders for glasses.

After I slice the object, it puts a thick hard piece of plastic in the lens area:

I’ve tried every option possible including optimal rotation, and different settings including removing supports, and for whatever reason this anomaly keeps appearing. I have no idea where it’s coming from, since my model is completely clear on that part as designed.

Any help would be greatly appreciated.

[m.kozlov]

Hello. We have checked the STL file and it looks like it had non-manifold edges. These problems need to be fixed before it will be possible to print the model correctly.