- Solved
See the picture. Whilst the update process is running, it's blank, but as soon as it finishes the text appears. I've tried using multiple browsers, Chrome, Firefox and Edge. All with plugins/extensions disabled, tried incognito window etc. I don't know why this happens. It started on 6.5.3 and now it still happens on 6.6.3.
I'm reporting this now as I just did a fresh install and it's still occurring.