My experience with gaming laptops points to the power supply not delivering sufficient power to charge the battery and simultaneously power the laptop while in use. Long term use can result in burnt a battery connector at the main board.
Therefore, I suggest you search for broken and/or burnt solder junctions in the power circuit. Look very closely as some may be covered by that black cloth tape often used to prevent connector disconnect during assembly, rugged use and servicing. Best of luck in your seeking a solution.