I've had my 2018 T6 shuttle since 2019. finally had a pop top fitted, rear aircon ducted to a vent on the RH Pillar, also kept floor level vents operating. However Aircon is not reaching the rear unit it blows well on hot air but nothing cooler than ambient. could it need re Gassing ? front seems to work ok but may not be as cold as used to be. its been worked hard in the recent heat.