Printer Help - how to handle a small step inside a cylinder  

Printer Help - how to handle a small step inside a cylinder

First, I have read @zoltan's post on how to ask for help but I am fairly new to 3D printing and this is my first post.  If I am asking something that has been answered elsewhere, please help me find it as I have tried to search the forum. Part of my problem may be that I don't know the vocabulary of 3D printing well enough but I am looking forward to learning.

My setup: Original Prusa Mini (4.2.1) - 8 months old with all the standard nozzle, Prusament PLA filament, Prusa Slicer 2.3.

My STL file is attached which I created in OpenSCAD.  I am using the 0.15mm Quality setting and have tried the suggestions in this post to reduce stringing.  detect bridging perimeters (on)

I am trying to print a very simple spacer with annular indents at both ends.  As you can see from the picture, I get a clean top with the small indent but the bottom indent has significant stringing and hanging threads.  I was hoping that the options mentioned above in v2.3 of the Prusa Slicer would help but no joy.  

Any advice on how to print this seemingly simple object?  Thank you

I was not sure how best to upload the files for the print so I created this ZIP file: Archive