Yep, start by cleaning.
Auto-shuckers poop where they eat, and some of that crap makes its way into the mag release/catch. The design of the P-series' fairly unique mag release/catch allows it to keep from fully seating against its stops in the grip frame if there's too much crud.
If cleaning doesn't help, contact Ruger or see if you can get the parts yourself (Midway, Numrich, Brownells, etc). But, keep in mind that the release/catch is two parts, plus the spring; and Ruger tweaked the design at some point (~1999?).
"Such is the strange way that man works -- first he virtually destroys a species and then does everything in his power to restore it."