Broken Feed with newsblur (works locally)

Hello,

I’m having some problems with the following feed:
https://www.gmuender-tagespost.de/rss/?startseite

it used to work fine with newsblur, but stopped working some time ago… if I try to suscribe to it in Reeder 4 (Mac) RSS-Mode (and not in newsblur), it works strangely…

any ideas?

Bernhard