We have a collection of wikis. A few of the documents can no longer be edited. When you click on Edit Page, the wiki does not get the line around it and it is not editable. The tools are greyed out. It does get the yellow bar across the top that says "Status: Checked out and editable." But it is not. And when you check it back in it returns an error: "Sorry something went wrong. An unexpected error has occurred."
In IE 11 I watched the scripts and when Edit page is clicked an exception is thrown:
Unable to set property 'ListId' of undefined or null reference