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For some reason, just turning one screw does not maintain proper alignment in relation to the road. Both screws seem to not adjust a "true" horizontal or vertical. There is a slight diagonal on which they are being adjusted. You really must use both screws to adjust.
My dealer, after having the vehicle 3 times, was incapable of aiming them. In fact, they aimed the beams lower not higher. I then spent about an hour in the evening properly adjusting them using both screws on both headlights. It consisted of many trips of adjust, drive and evaluate and repeat. As has been stated before, when adjusting, keep the driver headlight lower to not blind on-coming traffic. Just for a point of reference, my vehicle with improperly aimed headlights was built in Canada.
Good luck.