Marshmud: ok - what about trying to 'leave' that team by creating the respective link manually?
You would need to know the deleted fellowship's ID, but maybe there is a way to find it, and then insert the ID for the ### and the game ID for ***:
https://brainking.com/en/DoFellowMember?a=212&fid=###&tp=***

If the fellowship ID cannot be found, you could use Excel or something to generate a whole list of links with "...fid=1..." to "...fid=999..", and open them all.
I did something similar a while ago, and it worked perfectly - I saved the list of links in a file, loaded them as bookmarks into my browser, and then right-click 'open all'. it opens a gazillion windows, and one of them works as it should. just wait a bit and then close all.

...aside from the fact that all team members should be auto-released anyway when a fellowship is deleted... but no software is bug free.

Aganju: Exactly. I am about to delete a fellowship and will removed members manually before doing so aside from checking they are not in any teams before deleting.
I am clueless in doing that procedure with links
It would be easier to ask me to build a rocket to the moon
Although l know the Fellowship was the Good The Bad and The Ugly.
I have deleted ages ago any correspondence in messages l received from the fellowship which probably would have helped