Welcome to the forum unclebutch!
What you are seeing is droopage from a bridging, or overhang move. FFF (Fused Filament Fabrication) printing builds layer upon to create your object. In your sunglasses, the drooping you are seeing is due to the design. In that specific layer, your printhead is laying down plastic in mid air. Naturally, gravity will pull this down until it cools enough.
There are a couple of things you can do to help bridging and overhang moves. The first will be to increase your fan speeds, and slow down your print speeds. This will cool the filament as it comes out of the toolhead almost “freezing” the extrusion in mid air. (You will most likely still see droopage, but it won’t be as significant.)
The other option you can try is to turn on support options. This will build a structure underneath your object, to give these mid-air sections support to prevent droopage in specific locations. Now support is a tricky beast. You can define how close the object is in the X/Y plane and in the Z plane. The closer the distance the better the support will be, but the harder it will be to remove. Oppositely the farther away the support is the easier it will be to remove, but will naturally support less. (Something fine tuning for individual STL files is highly recommended.)
I think you will find a wealth of information in this forum, just don’t hesitate to ask!