What is cuasing these elements to stick out of miximo characters posterior please

Ive been trying to fix the issue I have where using mixamo animatiosn seems to dislodge the pivot from my miximo character actor reusltign in it goign all over the place when trying to rotate pitch yaw or roll.

The middle mouse drag the pivoit into character then right click and set pivot poitn has no effect, the character keeps leaving the pivot behind when the character walks saway or does anythgin.

i tried to follow this videon to add a root bone to try and stop the pivot detaching issue

as daf as 7.30 b mins but now gettigntherse deformities ie the tails with whatg Im guessing ad polygone dragging behind, how to I push them back ito her butt to make it smooth and whats causaing the problems, is it skin painting?

mins