Are you talking about the soft pad that comes with the RO 90 as standard or are you talking about the interface pads that you buy as a consumable?
If its the pad that comes as standard with the sander I guess it must have something to do with how you are using your sander. Have you tried using the hard pad (Blue) and if so are the results the same?
Do you have your extractor turned down low?
If its the interface pads, well it will depend on what you are doing with them, deep profiles, shallow curves, I think you need to give a bit more info for people to really help out.
by the way those interface pads are not really made to last, they take a lot of abuse for a thin piece of foam.