Demo "On-purpose 404 ajax call" appears broken

[Chealer]

The demo titled "On-purpose 404 ajax call" appears to be broken. When clicking on "Trigger global fail and change background to red", nothing visible happens that I can see.

Firebug does not allow tracing the fail event's callback, but it is executed. $loading does get the error class added, however $loading does not show.

[pocesar]

Is this in alpha branch or the master branch (that's 2.x range)?

[Chealer]

In 2.7.3.

I tried the demo a few more times and in one case, I saw a red rectangle appear in the middle of the page for a short time (couldn't see what it contained).