Active object selection - separate edge

Question

Somewhere during modeling something I did something that I am unable to find how to fix. When active selecting my car mesh in object mode I get this strange orange edge stripe, that I cannot account for. In edit mode I tried already selecting the edge and clear sharp and clear seam. Also mesh cleanup -> merge by distance but there seems only one edge. Because the mirror modifier the orange line appears also on the other side ;-)

What could cause this effect? And more important, how to get rid of this line that doesn't fit the outline of the car.

Answer 1

First tried to find out if it was an interior face, but it is only an edge I could delete. However I need the extra geometry for shading purposes. Then I was pointed to Non-manifold fixes from Gleb in a Bendernation post and with the addon '3D print toolbox' I found a way to fix the geometry by cleaning up 'distorted' faces. Some extra geometry was added and the result is that the orange line isn't visible anymore.