I am familiar with remotes that use a conductive paint on the buttom of the rubber buttons to "short out" PCB traces on the circuit board.These types of remotes are normally silent when the buttons are pushed and nothing is felt through the fingertips. You should probably be aware that cleaning these buttons slightly will sometime help their operation, but frequent cleaning of the rubber buttons will wash away the conductive coating and ruin the remote.

The 880 however uses the more reliable method of sticking an adhesive plastic film over the PCB. This film has small half bubbles with foil under them. When the button is pushed it in turn pushes down on the plastic bubble, causing it to collapse with a small popping sound, and the foil once again "shorts out" the PCB traces. By the way this type of button is almost total immune to cookie crumbs and slight spills because the electrical contacts are sealed under the plastic film.

In the case of the 880 it looks like this film may be lifting at the edges of the PCB, and that is why the volume buttons are the first to be affected.

Rick