mercedes benz ML air suspension

Mercedes » M-Class » 2006-2011
Question

Hi, I have a Merecedes Benz ML500, both front air bellows have been replaced in the past two years. recently the front passenger suspension has started lowering again, however when I raise the suspension to level 2 the suspension does not lower even over an extended period. Have you come accross this before?

I would like to fix the problem without being overcharged by the agents.

Regards,