Shimano makes awesome reels, but every reel needs a cleaning once in a while. I fully take apart the reel once a year and clean it before putting it up for the season if I only fish fresh water with it. However when I fish saltwater, it needs to be done more often. This also should be done if the reel gets dunked in water, especially saltwater.
This part also incorporates a quick cleaning where you just clean the spool and casting breaks.