Same problem here and I'm using a brand new aftermarket 65w power adapter. I was having this problem for a long time and i had to turn and twist the input jack to get it in the right contact position to charge. I purchased a new power adapter hoping it would resolve my issue, although its a little better, it's still a problem because i have to set a heavy object on the end of the input cable so it keeps contact during charging.
The only thing it can be is a bad DC input jack, or the internal power supply. Does anyone know where I can purchase those parts with installation instructions?
Thx