We were getting hammered on nofollow links. Someone made a change to stop putting the nofollow in and using JavaScript to traverse on interaction, but that person left sometime after the toggle went in and we discovered it had never been turned on much later, when we were rearranging our ingress load balancer and needed to tweak how we handled bot throttling. That was at least 10% of the requests during peak traffic and extended the duration of the crawls by a lot. So dumb.