On https://en.wikipedia.org/wiki/Talk:Ski-slope_nose we see Ski-slope_nose was chosen to be a redirection.
However the exact anchor has changed, so it no longer redirects to where people intended it.

Such situations could easily be avoided, if when when editing a page, a warning would appear:
"XXX other page depends on the ==header== that you are removing!!

Please, after saving your edit, immediately resolve that problem. Thank you."