The R1-S is designed to run on grass golf courses and absorb all variances in the level and quality of the ground it's running over.
If you feel your trolley is running not in a straight line then examine the wheels: all three should be securely locked in place, and particularly the front wheel - it must have both its locating lugs fully engaged.
Tests on surfaces other than golf courses won't replicate the conditions the trolley is designed to operate in.