When creating custom jockeys with commands or when a skeleton trap spawns the following mobs do not let their riders take control of their pathfinding and often they don't move at all unless they are pulled with a lead (there is probably some more apart from these): pigs, horses, donkeys, mules, zombie horses, skeleton horses, llamas, strides, slimes, and vexes.
ssue is not a duplicate as this issue is around all mob jokeys not working as aposed to MC-260974, wich is only about houres and skeleton hourse jokeys not working