Sorry to necropost but I'm not sure to understand your tutorial, what I'm supposed to do exactly when I found the problematic line in the consol?
My bad for the confusing instructions; here is a rewritten step 3:
Right click the problematic line (or really anywhere on the sources page). Click "Override content". It should ask you what folder you want to save it to, so create a folder on your desktop, then select that folder. If you did it right, you should now be able to edit the contents and follow step 4. Also, the little sidebar to the left of the sources content should show the page you are in as what seems to be a piece of paper with a purple dot at the bottom right.
If step 4 is confusing; removing "@next" should be possible by double clicking where the text is, which should let you start modifying the text. Then you can remove "@next".
If step 5 is confusing; CTRL + S should work to save the index. I do not know where a save button may be besides this shortcut.
Hopefully this clears things up.