Most recent item never shown in RSS feed

I'm having trouble with the RSS feed at http://ift.tt/1zMIuQL.

In all readers I tried (newsbeuter and Tiny Tiny RSS), I always get everything after the second item, but the newest one is never shown.

I don't have this problem with any other feeds, so there must be something wrong with that specific feed, but I have no idea what it is. The W3C RSS validator finds no issues, and I can't find anything which seems wrong either. This is how it looks at the moment:

<?xml version="1.0" encoding="iso-8859-1" ?>
<rss version="2.0" xmlns:atom="http://ift.tt/r5ut6F">
<channel>
<title>DayDeal Liveshopping | Ein Tag - Ein Deal | RSS-Feed</title>
<description>DayDeal RSS-Feed. Taeglich ab 9 Uhr erfaehrst Du als Erster vom neusten Deal des Tages!</description>
<link>http://ift.tt/1zMIuQM;
<language>de-de</language>
<copyright>Copyright 2010</copyright>
<atom:link href="http://ift.tt/1zMIuQL" rel="self" type="application/rss+xml" />
<pubDate>Mon, 04 Aug 2014 07:01:00 GMT</pubDate>
<lastBuildDate>Mon, 04 Aug 2014 07:01:00 GMT</lastBuildDate><item>
              <title>Elektro-Tischgrill</title>
              <description><![CDATA[<table><tr><td width="20%"><a href="http://www.daydeal.ch" target="_blank"><img style="border:0px" src="http://ift.tt/1o4TBAU"></img></a></td><td width="80%">Nur heute: F&uuml;r nur CHF 149.- anstatt 229.-</td></tr></table>]]></description><link>http://ift.tt/1zMIuQM;
              <guid>http://ift.tt/1zMIuQO;
              <pubDate>Mon, 04 Aug 2014 07:00:00 GMT</pubDate>
              </item><item>
              <title>Reifen-Kontrollsystem</title>
              <description><![CDATA[<table><tr><td width="20%"><a href="http://ift.tt/1kh0RJO" target="_blank"><img style="border:0px" src="http://ift.tt/UM3Uy0"></img></a></td><td width="80%">Nur heute: F&uuml;r nur CHF 99.- anstatt 169.-</td></tr></table>]]></description><link>http://ift.tt/1o4TBB0;
              <guid>http://ift.tt/1zMIsrW;
              <pubDate>Sun, 03 Aug 2014 07:00:00 GMT</pubDate>
              </item>
              ...

The <pubDate> and <lastBuildDate> tags look okay to me (they are both after the most recent item), and so does the syntax of the first item. I'd like to report the issue to them, but first I want to understand what's actually wrong.