I saw that yesterday too. Only because while scrolling I fat-finger tapped it and got an error page which made me look. I was going to screen capture it if I saw it again and then post about it. I kept an eye out for it, and when the topic got another reply it again showed in my suggested - but - it showed “hetzner” and not “undefined”.
So it appears that not only was the link text not getting into Suggested, but neither was the link URL. As for it being OK the second time, I don’t have any idea.
* I can’t recall if it was a new or unread, but I’m leaning towards it having been a new.