I bought a nearly new Logitech G710+ very cheap on eBay and it worked great for several days. Then, the Enter key became rather flaky: half the time, it would not register at all, and the other half it would register twice. The seller offered to exchange it, but since it shipped from the US and the exchange was going to take ages, I decided to try to repair it instead.

This keyboard turns out to be pretty easy to disassemble. There are no hidden screws anywhere, kudos to Logitech for that. They like to place screws under stickers or rubber pads on cheaper keyboards, so it was quite a relief. First remove all the screws from the back, then unclip the front face. It didn't come off without a fight, but it wasn't the worst either. It's not held by anything other than the clips and the visible screws on the back.

The trickiest clips were just above the arrow keys, here's a photo of where they attach:

Watch out for the cable connecting the volume wheel to the main board:

With the front removed, you can access the four remaining screws holding the main board in place:

Disconnect the USB cables and you're done!

Now flip it over, and tada! Here's the problem:

This pin is supposed to be covered with solder like all the other ones around it. That tiny amount of solder connecting the pad to the key must be how this keyboard passed quality control at the factory... I had actually ordered a spare switch, thinking it needed to be replaced. That ended up being unnecessary. All that was needed was to solder the pin to the pad properly:

It's working great now!

By the way, the keyboard works perfectly well with all the plastic removed. When it sits with the board directly on the desk, it is so much nicer to type on that I was really sad to have to put it back together, as it doesn't look like it will last a long time without the bottom. I've always thought that mechanical keyboards are a bit too tall for comfortable typing; this has removed all doubt. The keyboard is almost 1cm shorter without the plastics.

And another thing... It really looks like the pass-through USB connector can be used to make a detachable cable. It's probably not connected to anything other than the cable coming in, so in theory, all one needs is to connect those two white connectors together inside the keyboard. I'll have to try this when I get a chance. I've done it and it works!