I do a lot of group rides. Often there’s some jokers ahead of me that are doing circles. How is that done or why? I’m guessing they have run far ahead and wanted the pack to catch up. In companion there’s no buttons to do this.
Donuts are a long-standing bug. It’s probably not intentional.
It’s another “random” Zwift thing, along with shadows doing their own thing. I personally dislike it when a rider cuts across the grass on a corner
It’s usually to do with communication issues with the Zwift server, either theirs or yours. It’s your Zwift client struggling to figure out their exact position.