How to fix Thunderbird crashes while retrieving RSS feeds

This was a strange case of the Thunderbird email client crashing while retrieving an RSS feed.

Every 10 minutes Thunderbird would crash while retrieving RSS feeds.

After making sure that I was using the latest version of Thunderbird I restarted the application with add-ons disabled but the problem persisted. This led to the conclusion that the cause of the problem was one of the RSS feeds. 

I checked all RSS feeds and noticed that all feeds below one were stuck at a previous date.

I left clicked on that feed and pressed get messages and as anticipated Thunderbird crashed. This was the problematic feed. Then I left clicked on the feed again and then pressed subscribe, copied the feed url and checked it in an RSS validator.The feed  did not validate and this caused the Thunderbird crash. After deleting that RSS feed Thunderbird stopped crashing and hasn't crashed since.