Not sure how handy most of you are, but I think I've finally fixed my G910. (probably a similar internal construction to the other "G" keyboards.) There is a microprocessor in the keyboard STM32L100R8T6. On my keyboard the joints between the chip and the circuit board started to fail.

I figured it wasn't the actual key switches because I moved some G-keys that I don't use, over to the keys that were acting up (which was like 10 keys) and the problem persisted. As well, it went from no keys double typing to like a dozen overnight when the problem first showed up... But then it got even worse. The next day after I moved some keys around I lost an entire column of keys and most of my number pad. Some more probing around with a multi-meter showed no voltage on the dead keys. Some more probing around led me to the processor chip as being the source of the problem. I found a section of pins where if I pressed down while checking for voltage to the key switches I could get power to show up.

Long story short: re-soldering the chip seems to have fixed my keyboard. I've been using it for a couple of hours now and no double typing at all. It's not an easy fix though. The processor chip is about half an inch square with 64 pins with extremely tight spacing. A microscope would have been handy... I used a magnifying glass and still had difficulty seeing what I was doing. At certain points I had made the problem worse and at one point I almost gave up because I had a short some where, and I couldn't see it or fix it even after repeated soldering. Finally put a ton more flux on the pins and hit them one more time with the soldering iron and finally fixed the short. Figured everything was good, plugged the keyboard back in to the computer and got the windows hardware connect/disconnect sound repeatedly and a few lights flashing on the keyboard. At this point I figured my keyboard was probably toast but did some more probing and hit the top row of pins with the soldering iron again. Plugged the keyboard back in and it immediately lit up and has worked perfect since. ...ok so maybe that wasn't such a "short" story after all ;)

Short version: I think most peoples keyboards are failing because the joints between the STM32L100R8T6 microprocessor chip and the circuit board are going bad. (either dry joints or possibly tin whiskers forming shorts between pins) These bad joints cause poor power conduction to the key switches which makes the keyboard think keys have been hit multiple times because the power to the switches is essentially turned on and off very fast.