I recently bought a brand-new, genuine Magsafe 60W charger for my mid-2010 MBP (my previous charger died suddenly after months of extreme fraying). Within a few hours of using it, strange and bad things started to happen. First, the battery intermittently stopped charging despite an amber light. Then the light started dimming and flickering, and the connector started heating up a lot. Finally, it started completely failing to charge, with no light.
However, I then discovered that if I very carefully hold the cord in certain positions and apply tiny amounts of force in various directions, it charges completely fine. I thought this might be a Magsafe port problem, so I replaced the Magsafe port, but the problem persists. I also tried resetting SMC many times to no avail.
What could be the problem here? Is it more likely to be a charger problem or a logic board problem?
One thing I did notice is that the pins don't quite seem to line up exactly with the connections in the port: they're offset sideways by 0.3mm or thereabouts. It's a long shot, but it might explain why the charger only works when pulled in a certain direction. Is this a known issue?