When I Add or edit a post, the list of categories no longer appears and the featured image doesn’t show on existing posts any longer, it just shows loading icon forever.
The only way I am able to set the category is to use the “quick edit” option.
Not sure exactly when this broke as I don’t post on my blog very often.
This is on a multisite installation and it only appears to be affecting the primary site. The other sites are not having this issue.
All sites use the same theme and mostly the same plugins.
I have tried disabling all the plugins that are enabled on this site only, to no avail.
Obviously the network enabled plugins are enabled on all sites, and as I mentioned, other sites are not having this issue.