I had the same problem awhile back where I couldn’t post comments and the editor would load perpetually. Turns out it was due to a Firefox extension I was using. I’d suggest maybe switching browsers and/or disabling the problem extension to find the problem, if this is the case.
Okay, that wiki's site JS is a mess. Looks like it was causing issues for VisualEditor a few months ago but it probably hasn't been fixed yet. Try contacting the admin who most recently worked with JS on the wiki and if they are not sure how to fix it they can contact a Staff member to help them fix it.
In the meantime, you can edit pages on that wiki by appending &usesitejs=0 at the end of the page URL when editing with VisualEditor or use another editor.