Some group pages are showing 'Page not found' screen - no idea what caused this?

Hi, on my site YNFA.NET i was working on a caching plugin when suddenly I realised i could not go to my profile page or some group pages from the navigation menu. Some group pages are fine but not 'YNFA Hub' or 'Extreme Hub'. Seems to be a disconnection somewhere and i have no idea how it happened. Seems unrelated to what i was working on. I have tried rebuilding the permalinks but this has not worked. Very worried.

I have enabled access to the backend. Could you pls look for me and solve this for me.

Msany thanks