Trying to add an RSS feed results in an "Unhandled Error"

Hey friends, is there any way to find out why a particular RSS feed is having issues? It loads fine in the browser.

The feed in question is Untitled

I’d check it with this, it does reveal something, and it says “This feed is valid, but interoperability with the widest range of feed readers could be improved by implementing the following recommendations”

Weird! It seems to have added itself in my feeds, twice!