Spaces: Error occured while trying to proxy

When working with essentially a copy of an existing space I have, it gives me the following error, despite the code & everything else seeming to work (checked the logs). Tried clearing cache and refreshing, different devices, changing my theme, etc… nothing.

The public space that I made a copy of is this one on my profile. Any ideas?

pinging @cbensimon and @chris-rannou on this!

Oddly enough, when I checked this afternoon it seems like it fixed itself, without me re-pushing?

No pressing issue at the moment, of course, but I guess any advice on what to do next time (if there is one) would be great!