Hi @harryshapes,
I visited your group lists page and it seems like the issue is not happening to me. Is the issue still happening for you?
In any case, for that kind of issue I would recommend to first clear your site’s cache if you are using any caching plugin (like WP Rocket of W3 Total Cache), and then regenerate the permalinks like you did.
If that still doesn’t resolve the issue, please try to disable all your plugins except BuddyPress to see if it fixes it. If it does fix it, you will then have to re-enable your plugins one by one until you find the one that is causing the problem. Once you find the problem plugin, you can either try to update it, disable it, or contact the plugin support to see if they can help.
Hope this information helps you.
Best regards,