Diagnosis
Metal debris is inside the gear housing and around the anvil. It will cause accelerated wear.
How to Fix It
Remove the battery. Use compressed air to blow out debris from the front around the anvil and through the rear vents. Hold the tool with the front facing down so debris falls out. Do not disassemble unless you are trained.
If That Didn't Work
For packed-in shavings, a soft-bristle brush (like a clean paintbrush) can help dislodge them before blowing with air.
Heads Up
Never use water or solvent sprays. They can wash grease from gears and corrode internal electronics.