mobs get stuck on fences

Me and my friends were playing in a world and there was a savanna village and some of the villagers would get stuck and start jumping right be side fences and wouldn't move also the same thing with cats they were the only mobs I noticed doing it but there could be more also I know it says only bugs or something like that and make another one and maybe there's a reason why but why is there jungle skins for the villagers when there's no jungle villages