Maybe it’s still using the borked config because all sessions were not exited? Try exiting it and then make sure no tmux process is still running, by for example running ps -aux | grep tmux.
Otherwise there must be some tmux config still lying around in your $HOME.
Edit: I don’t know anything about Macs so I’m just assuming it works similar to linux.
Does fzf search hidden folders? You could also try with this, to make extra sure: find $HOME -name "*tmux*".
Codeberg looks pretty good at a quick glance.