RSS feed dates out of order issue

I am a developer for a website called RedRoom who use WordPress to blog there poetry. Everything has been fine for about 1.5 years up untill now.

What is happening is the RSS feed is showing all the old entries and not the most recent but if you navigate to the page with all entries through a browser the order is correct. Previously the RSS feed had the latest dates at the top but that is no longer the case.

The URL for all the site blog entries is:
https://www.redroomcompany.org/wordpress/?cat=9

The RSS feed link is:
https://www.redroomcompany.org/wordpress/?feed=rss2

Anyone have an idea as to what is going on as this is an important feature to my client and the last thing I want to have to do is reinstall wordpress only for it to happen again. The strange this is we didn’t make any changes at all.
Any help would be much appreciated.

Redroom Developer