Fixed.
There was indeed a JavaScript error, due to some user activity item existing for a post that didn't exist. This is likely due to @Majidcs posting in a discussion that was later deleted; I believe I've fixed this in our dev version.
To make matters worse, Mithril had a bug that prevented any further redraws after it encountered a JavaScript error during a redraw – hence why none of the buttons would work. This was fixed a while ago, but this dev forum isn't up-to-date yet. (Soon!)