The character on the bottom controls the character on top. They are attached by a rod constraint. The character on top is completely massless, yet this sliding still happens.
The feet on the character on bottom have Friction = 2 and FrictionWeight = 100 and the part that the character on bottom is standing on has the same custom friction properties (i.e. the max friction possible).
I would just anchor them if I didn’t want them to move. The problem is I want the player on bottom to be able to walk around and see no effect of this sliding.