kairoeder on "[Plugin: WP RSS Aggregator] Can't import feed from a w3c valid xml"

Hey,

even though the following URLs seem to be valid (checked with the w3c validator) I get an XML parse error and even with "force the feed" I can't load them.

Here's an example feed
http://publishingperspectives.com/tag/uk/feed/

I tried it on two servers, both not working but other feeds do work.
This sounds more like the XML from "publishing perspectives" is broken but why does the w3c validator tells me it is correcnt plus other rss feed reader are able to load posts from this feed?

Debugging sais:

[24-02-2016 18:36:01] [Error] WPRSS > wprss_get_feed_items:
Failed to fetch feed "http://publishingperspectives.com/tag/uk/feed/". This XML document is invalid, likely due to invalid characters. XML error: Mismatched tag at line 30, column 117

Any ideas how to fix this?

Edit: here's the validator Link https://validator.w3.org/check?uri=http%3A%2F%2Fpublishingperspectives.com%2Ftag%2Fuk%2Ffeed%2F&charset=%28detect+automatically%29&doctype=Inline&group=0