Now I get your point 
As you can see the new group started before end of August.
The old one was kept open for reading the next month.
The fixed links are the ones inside the new forum.
I don’t know what rules discourse have for this, but maybe it is possible to create a “new group” with the exact same name as the old one, with just one post telling where we are now. And read only!
Or maybe there are a homepage setting which could redirect the old name (and maybe other misspelled options) to the new forum.
The last option (if possible) would be better solution, for solving the problem you point out, with redirecting all links from any other forum, where old agopengps links has been added.