Not sure what has changed, but it seems that the latest updates have broken some things:
###The discourse-bbcode-color plugin.
I believe I’ve narrowed it down to the discourse-bbcode-color plugin spitting this error out:
TypeError: undefined is not an object (evaluating 'Discourse.Dialect.addPreProcessor')
###/admin/backups is broken and gives:
Error: Something you did caused a view to re-render after it rendered but before it was inserted into the DOM
EDIT: this error seems to go away if I disable the discourse-bbcode-color plugin.
###discourse-data-explorer plugin breaks /admin/plugins.
I believe this error is related to the discourse-data-explorer plugin:
Error: There is no route named adminPlugins.explorer