06 R350 airmatic problem Code 5503

Hi guys,

I have here 2006 Mercedes R-350 airmatic. Car has both new front air-bags, and a new compressor. After driving for a while the warning light "Visit Workshop" comes on. The code is 5503(Recovery time during filling of centrsl reservoir is too long) in the suspension module. There is no air leaks. after cycling the ignition the light resets ,and comes back after driving. The only think that I have noticed questionable is the rear level sensor. The pivots have rusted a little and the plastic rod isn't all that easy to move on its pivots. I have removed the links on both sides cleaned and lubed them. Moves much easier now, but after driving light still comes on. I also took noted on the sensors reading :

LF :38mm
RF :38mm
LR :42mm
RR :36mm

This was the first readout with suspension at normal height.

LF :46mm
RF :44mm
LR :49mm
RF :39mm

This is with suspension fully raised.
The suspension seems to be working fine, just that warning light keeps coming back. What else could cause this ? I have also checked the wiring as per the bulletin. All looks good. The fuse was never blown. I never replaced the relay, could that be the problem?

Thank You