Can anyone here sprint, run forward, jump, and then after you stop moving try this command on 1.21.11 papermc?
/data get entity @s Motion
Something about my world and plugins is causing this to stop resetting x/y to 0. I have to do more testing tomorrow but something is fundamentally broken in my setup because I wasn't able to replicate the issue in vanilla, bukkit. or spigot yet.
Just paper with my specific world file, nothing to do with datapacks either as far as I can tell as I haven't included any.
Basically I've tried replicating the issue by dragging over each plugin which had no luck. I copied over all the configurations for all plugins and that didn't cause it to happen either. Then I copied over the world file itself and suddenly the issue began to replicate.
I'm at my witts end!