So, I've been having some issues with my original Game Boy. One was the vertical lines issue on the screen, but I fixed that already. The other issue is strange, and I have no idea how to fix it. Basically, the controls are all over the place. Like, every direction on the d-pad presses down, and also the start button sometimes presses down, too. Select button presses up on the d-pad most of the time. I think B and A are okay, at least. Heh.
Edit: Now B and A are pressing left and right...
Edit 2: I should note that the controls were already acting up well before I ever opened the Game Boy up.
Edit 3: It's the ribbon cable causing the issues. Everything seems to be good now except for up on the d-pad, which I just cannot get working.