I think I found the article!
https://phys.org/news/2022-11-physics-sheep-flocks-alternate...
https://phys.org/news/2022-11-physics-sheep-flocks-alternate...
https://www.yahoo.com/lifestyle/a-flock-of-sheep-has-been-wa...
Humans exhibit the same general behaviour, but followers are more (read, at all) likely to notice they're going in a circle and break off. (Usually quite quickly.)
0: youtube-dl https://www.youtube.com/watch?v=nGlzoT0sLaM
https://www.newsweek.com/mystery-sheep-circle-china-12-days-...