I had this too, this week, just a white blank screen appeared. I needed several attempts to get some text. As I was in the mountains, I thought it was my internet connection. But after a few hours everything was normal again.
If someone is working on the forum themes (possibly in response to the recent enquiries about the dark theme) and accidentally commits the changes to the live site before they’re finished, this is what happens. Simple mistake, but nothing to worry about.