Changing a Motion of Player-rided mobs using /entitydata : Wrong moving

https://youtu.be/76c610UrX2U

Used command : /entitydata @e[1201,63,-1160,dx=0,dy=6,dz=0,type=EntityHorse,tag=spawndeco_ready] {Motion:[-1.3d,3.0d,-0.4d], Invulnerable:0, Health:1.0f, Silent:1b, CustomNameVisible:1}

Sometimes mobs moves wrong direction.

Never used any other commands into those horses like /tp, /entitydata, etc for moving. (Those explodes are /playsound and /particle) Used only this command.