`Run` returns `Unexpected token '<', "<!DOCTYPE "... is not valid JSON`

[xobs]

When going to https://play.rust-lang.org/?version=stable&mode=debug&edition=2021 in a new browser, hitting "Run" returns a compile error of:

Unexpected token '<', "<!DOCTYPE "... is not valid JSON

The actual response looks like a timeout error that the site is trying to parse as some sort of JSON message.

[xobs]

Ideally, the program would detect an abnormal response and report an error with the backend. Status information would be nice. I wasn't sure if it was an issue with my code or an issue with the backend, as there is no indication that there is a problem on the server side.