Face where there should be no face When importing this .stl file in Creality Slicer another face appears in the middle when viewed in layered view. This face is not visible in my 3d modeling software Blender. I tried cleaning up the model a bit and to triangulate the faces myself, neither helped and the problem is still there. Also I didn't find anything online.
At the intersection of the top and bottom planes of the cross-piece and the cylinder, there are non-manifold edges. Meshmixer is able to identify this problem but cannot repair it. My slicer, Simplify3D also identifies the faults and prints a solid cylinder between the planes. Prusa Slicer 2 also creates a solid at that location.

As you've indicated that you are the creator, consider to use the 3D printing features within Blender to assist you with repairing the problem locations.


  File ‣ User Preferences (or Ctrl-Alt-U)
  to open the User Preferences menu.
  
  In the Add-ons tab, start typing 3d print into the search bar. Once
  the “Mesh: 3D Print Toolbox” shows up, click the checkbox on the far
  right to enable this add-on.
  
  Close the User Preferences window.
  
  In the Tool Shelf, there should be a new 3D Printing tab.