Through the menu view > hidden geometry and using the option show endpoints temporaly you will be able to understand better what’s happening.
You will see several lines with dots, they’re are edges that are soften and smooth.
You could make all of them visible with the eraser tool + control + shift
You can soft and smooth them with eraser tool + control
The lines you see are connecting the edges and with the arcs
What I did to fix it was using the eraser tool holding the control key that works as modifier and lets you soft and smooth those edges.