Adjust the lower roller (A).
Remove the roller maintenance cap (B).
Slightly loosen the lower roller bolts (C).
Move the door up or down to equalize the gaps.
Tighten all bolts securely, and reinstall the cap.
Honda Odyssey Service Manual > Rear A/C System Description: Rear Heater-A/C Door Positions HOTCOOL(VENT)(HEAT/VENT)(HEAT) ...