Lines in stl file

My caster says there’s a problem with the stl files creating these fine lines. Is there any way to prevent this? Or save as 3dm which is what they’d prefer?

Not sure about which lines you are referring to?

Can you please send the STL file to support@shapr3d.com, along with your tolerances (see pic) We will take a look

As for 3dm - we don’t support it