Inset pulling along wrong faces I'm following a PluralSight Blender fundamentals course. It's my first attempt at using Blender, love it so far!

However, during the course I have to inset some circles. This worked perfectly until I accidentally deselected the right faces. Now when I re-select the faces and try to inset them I get this weird result.
It looks like some faces are somehow connected to other faces?

It supposed to be a circle, like most of it is. 

Been fiddling with this for over two hours. Any help is appreciated!



After using Clean up -> Merge by distance I get the following, interesting yet unwanted, result. It looks like still something too much is being selected.
This looks like non-manifold geometry.


Check possible interior faces through Select > All by trait > Interior Faces
Get rid of them through Delete > Faces
Select all and remove double vertices through Mesh > Clean up > Merge by distance, Alt + M


Remove interior faces and double vertices left behind.