Tabs disappeared

The tabs across the top of the wiki post for 'Page Discussion History' have recently disappeared.
eg https://podiapaedia.org/wiki/sports-medicine/

They only recently happened for me and not linked to any theme or plugin in update.
However, when I search the Google cache for some pages, it appears as though it has been like that for a while (perhaps for non-logged in users)

Not sure where to start troubleshooting this. Any idea?