Be sure to inspect the metal connectors to see if they're stuck or fail
to have both halves fit correctly; sometimes the metal part gets stuff
in there that may not easily be removed with a dry brush.
Learn about using the Apple MagSafe Adapter included with your Mac
notebook computer and get tips for reducing wear on the adapter.
Be sure to regularly inspect and clean both the MagSafe adapter connector
and the power port on your Apple portable computer for dirt or signs of damage.
• Reduce cable strain on your MagSafe power adapter - Apple Support
There are a suggestions in iFixit.com repair guide DIY damaged MagSafeadapters.
Another thing, if internal Mag connector inside the Mac is bad: it can be replaced.
Part is known as 'MagSafe DC-in Board' is separate logic board. ~ Level: Difficult.
• MacBook Pro 13" Unibody Mid 2009 'DC-in Board' Replacement - iFixit
Good luck & happy computing! 🙂