You are correct, the rectagular boxes are the microswitches. It doesn't surprise me that oxidation or even just dust and skin oils could lead to these buttons not working. I've always just replaced the microswitches entirely if they fail or go on the fritz; assuming the the microswitch can be opened up, cleaned, and put it back together, then I don't see why not give it a try

Disregard the first part of my comment. I have the measurements from the shell screws

On mine they are M2x10.25mm screws. The head looks to be about 3.25mm wide

Hi Sophie. I unfortunately cannot find the shell and screws of one of these mice.

I would recommend trying one of the shell screws from one of the bottom holes and put it in the hole under the right click or the front hole, depending on which is missing

The microswitch may also be on its way out; a “bounce” click when you click and hold is a good indication of this

From my measurements with a non-digital caliper, it is approximately 9.5mm square, with a height of approximately 1mm

If measuring from the outside where the component is indented for the contacts, it is about 8.5mm. The button looks almost like a very stubby “+” symbol. I hope this information helps!

I find that the easiest way to desolder them is to heat up the existing solder, add more new solder, then use a desolder vacuum pump as close as you can to the pin while your iron is still there. If there's still a small residual amount “tacking” it on, heat up the pad around the hole and then wiggle the switch around

It helps to have a helping hands station and a pair of tweezers or hemostats to hold the switch, as the switch and pads will get hot

That’s a good switch to replace them with

Me personally, I like to pull the switches off of other mice, like those rebranded Logitech ones that are bundled with some computers

The G502 is easy enough to pull apart and put back together that I don't mind replacing the switches on occasion

You are correct, that is the middle mouse button

Thank you for these instructions; I used them to pull a the drive for destruction. Without these I wouldn't have known where to being!

I found it far easier to remove the right button by squeezing the part where the hinge is (near the back) with tweezers, which unpegs the hinge. Then you just lift the hinge part out the back, slide the button forward slightly, and then remove it

I used this guide to replace the batteries on a 2GB and a 4GB Nano. This is a great guide with good attention to the important details. These are also much easier to take apart than 4th generation Nanos from my experience.