I just 5 minutes ago got a forum group mention event, so I clicked the forum in question.
https://subeta.net/forums.php/read///1/#
^That is where it took me. It is a closed thread from 2014, not the nice shiny new thread I was trying to get to. The user who pinged never even posted on the old thread. Not sure what happened there but it takes me there any time I click.
[Edit] I would like to add that it doesn't even show on my recent pings page either.
[edit] 2nd edit here. It appears that the thread I need to go to was eaten by the site, but I'm not sure if that is why it was doing it. I now get "Oh No! Sorry, no post here was found..."
My post about the broken link.

This happens to me too. I got the first pings yesterday. 4 more today, all for the same board... but keeps leading me to the dead thread about HTML help. I tried searching for Delphi yesterday... but the user didn't exist. Found the board today.... https://subeta.net/forums.php/read/922698
[edit] So, this happened again to me (2/20/22), except it was my board and my ping that was directed to this old board. ???