I'll start. I was trying to clean my fat PS2 from the inside. I accidentally broke the ribbon cable that connects the power/eject buttons to the motherboard (the cable is very long and super annoying, it's one of the biggest design flaws of the fat PS2). When I assembled it, the power LED didn't light up and the eject button didn't work. The console was powering on and it worked fine, though. A few months later I painted the case, so I obviously took it apart. After putting it back together in the newly painted case, it didn't power on. Turns out it was the long ribbon cable. It was broken completely. I fixed it by just buying a new ribbon cable and all issues are fixed now.