In most cases, it does not slip. There are 3 key reasons why.
Electronic anti-slip control. If slipping is detected, the motor torque modulates similar to how ABS system works in a car.
Active suppression system. Rubbee X is pushed to the tire not only by it’s weight, but also with a 200N pneumatic cylinder.
Special roller. Both material, shape and surface texture of the roller is optimized for increasing grip in all weather conditions.