Leaking air struts - Replace them with Arnott units, and do both sides. Do it somewhat quick, eventually driving on that leaking strut will burn out the compressor seal, and then you'll need to either replace or rebuild the compressor (ask me how I know) - a visual test can confirm whether its leaking, just get under the car and look at the bag, it will probably have small micro cracks on the bottom fold.

Just confirming, the side raises itself when the car is started? Or it pumps itself up when the car is not running?

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards