Fixing things you don't understand

I don't really get how any of this works. So far I've just been doing things and they've been working OK most of the time. Building Whimsy has been an education because there were some problems with the traces so I ended up having to cut some and manually connect them. Never done anything like this before (and it certainly wasn't me who diagnosed it!), and amusingly it wasn't even the cause of this issue.

I've had a chattering Y key on this board, and it's very annoying. To make matters worse, it's also intermittent. I decided last night to have a look at fixing it. I don't really know what I'm doing, but there's a limited number of things it can be:

• Something wrong with my manual traces
• Problem with a diode
• Dodgy joint on a switch
• Firmware

I disconnected and reconnected all my manual traces, and replaced their wires. I recut my severed traces. I reseated my diodes. I changed the chatter threshold on my firmware. None of that fixed it. Which is a shame because I don't like desoldering switches, but there you go. Fortunately when I went to desolder the offending switch, I noticed that it wasn't properly joined to the pad. I heated the joint and added some more solder and tested it and that seemed to fix it! So that was a fun little Sunday evening task I suppose. It's very satisfying fixing things like this. Especially when it was my own questionable ability that caused the issue in the first place!