Attach physical animation problem...!

Hi Guys;
During runtime, I spawn and attach an actor as a " Tail " , to my AI_Pawn .
when my AI-Pawn is not moving, everything is fine ( I mean pawn tail is hanging down ) , but the problem is , when I move the AIPawn , using MoveToLocation() function, the physic simulation of the Tail becomes very slow and incorrectly …!

Thanks for helping.
MSD.