This bug has been in the game for years. I've reported it on multiple occasions.
The bug occurs when you have any amount of extra movement speed above 100%, and occurs with most personalities that modify the jogging animation. The personalities that do work with added movement speed are Zombie and Jester (and maybe Drunk? I don't remember if that one works) but others like Assassin, Thief, and Worm Wizard revert their animations.
The bug has been around forever despite multiple reports. Don't hold your breath on it getting fixed because it seemingly doesn't matter to the devs.