I posted this some time ago, but I'll put it up again for anyone that didn't see it and is experiencing this problem. I did this to my 2014 329DS. It still creaked and popped for a couple of weekend trips but then it stopped and I haven't heard it since. I used the Maxima Motorcycle Fork Oil (you can get it at most motorcycle shops).
I spoke with a Lippert rep and they are well aware of the problem. Here is the solution he sent me:
ADDING ANTI-STICTION FLUID TO LCI HYDRAULIC SYSTEMS
1. Torco RFF Grade 15 (Fig. 1)
If there is a popping noise in a Lippert Leveling system, Lippert has approved adding a quart of anti-stiction fluid. Approved fluids are listed by brand name and fluid characteristics below:
2. Maxima Fork Oil Grade 15 (Fig. 2)
3. Caterpillar Hydraulic Oil Additive 1U-9891 (Fig. 3)
For maximum results in the shortest amount of time, please follow the preparation and procedure exactly as written below. Failure to follow the preparation and procedure may result in delayed resolution of the audible disturbance.
1. Obtain a clean container (large enough to hold a quart of fluid)
2. Obtain a fluid extraction device (siphon, turkey baster, etc.)
3. Fully retract all hydraulic cylinders and jacks.
1. Using the fluid extraction device, remove one quart of fluid from the power unit reservoir.
2. Add 1/2 quart of the specified fluid.
3. Extend all hydraulic cylinders and jacks fully.
4. Add the remaining amount of the specified fluid.
5. Fully retract all hydraulic cylinders and jacks.
6. Run the Auto-Level feature on the Level-Up system per the instructions found in the Owner's Manual.
If the noise persists, the addition of a second quart may be necessary. Follow steps 1 through 6.
Fig. 1 Fig. 2 Fig. 3