I am subscribed to this feed: https://www.lightbend.com/blog/rss.xml

The feed contains over 300 articles and all of it was marked as being unread several times. I suspect it happens whenever a new article gets published, but I'm not sure. I woke up to an inbox filled with this feed's articles several times.

Initially I suspected it's the feed's fault. Maybe they don't use stable guid (like it happens with poor implementations). Maybe they have a modified attribute that keeps being updated. But I couldn't find such evidence. Why is this item, for example, being marked as unread, given pubDate and guid haven't changed?

<item>
<pubDate>Tue, 23 Mar 2021 14:59:00 +0000</pubDate>
<title>Akka Workshop Series: Build Cloud Native Microservices on Kubernetes (5 Parts)</title>
<link>https://www.lightbend.com/blog/akka-workshop-series-build-cloud-native-microservices-on-kubernetes-5-parts</link>
<guid>https://www.lightbend.com/blog/akka-workshop-series-build-cloud-native-microservices-on-kubernetes-5-parts</guid>
<description>
...
</description>
<content:encoded>
...
</content:encoded>
</item>

I have approximately the default setup. I don't have mark updated articles as unread on.

Version: 1.18.0 installed via the official Docker image.