I was also getting the weird movement going on in my version, as others have very helpfully pointed out in other threads this was caused because our player collider is a ball, and it was rolling around. The solution was to lock rotation in the X and Y axis on the collider (in the blueprint, under the physics tab and under constraints). This fixed the sliding, but… I was also getting pushed around by things I picked up.
The solution to being pushed around when picking things up is to increase your reach distance on the grabber. The problem was that my reach was less than the size of the player, so chairs and stuff were getting shoved into it and moving the player.