btw You'll get a sharper edge on the mouthpiece if you enable single extrusion walls. Unless you already have it switched on, that is! Advanced tab....Thin wall behaviour.
I had a weird artifact when I exported an STL from Fusion 360: there was an extra line extending down from the bottom of the model that caused the model to float above the virtual print bed. Sure enough, it tried printing that way too. The tool I used to fix it was Meshmixer. I used the Auto Repair All function in the Analysis>Inspector panel.