If you continue to get UI errors in game, you may have an outdated add-on running.
You can follow these steps in this specific order to remove add-ons:
Exit the game
Navigate to C:\Users\<username>\Documents\Elder Scrolls Online\live in Windows Explorer
For Mac systems, you will find this folder here: ~/Documents/Elder Scrolls Online/live or ~/Documents/Elder Scrolls Online/liveeu/ if you are in the EU server.