3 months after purchasing G502X, I got this issue. What I can see is the left & right buttons dead at the same time even though I didn't have any business with the right button. So, I dig into its hardware.
My job is a hardware engineer, but not for mouse. My below writing may have difficult for most people because it is more about technical.
The G502X have many buttons, but only the right& left button are light switch, others are mechanical ones. The light switch has 6 pins, but only 4 small pins actually needed, 2 big pins does not have any functions.
2 in 4 pins are for the LED and the others 2 are the switch for the signal to controller.
The LED is always ON (.i.e light on), so when you press the button, the light from the LED goes to the switch side and we have the signal left click (see the advertisement video to see how it works).
I discovered that, it looks like the LED side in the switch have too much current, and this cause the LED is hot. In my case, both Left & Right switch is dead permanently because its LED is dead.
This also explains why "the left & right button dead at the same time even though I didn't have any business with the right button", You do not press the buttons, but the LEDs are still light on and overcurrent.
Now, to fix it, I replaced these switches with Omron switch D2FP (5 pins) or light strike LK (6 pins) switch and inserted a resistor (330 Ohm) on the LED side for each button. Until now (~1 year) after my rework, the mouse is still good.
The hardest part when reworking is not about circuit, but this mouse mechanical, disassembly and assembly it is a nightmare, too many screws and plastic parts.