I've got my HiDefNES installed in my front loader and all seemed to be fine. After a few hours of playtime the image starting scrolling left and wrapping around the right side of the screen. I have no idea what's causing the issue. I resoldered everything and the issue stopped, but when I started it up today the image was scrolling again. Again I resoldered and it's working now, but I'd like to find the cause so I fix it for good.
I should note that the pads for pins 15 and 19 on the PPU were partially pulled. No idea if this is the cause of my issue. There is some metal there and the solder joint seems stable. I'd just run a wire from the pins to ensure a solid connection, but I can't read these NES schematics to save my life.
Pin 15 of the PPU is not important, it and pins 14, 16 and 17 were grounded on the NES and are only connected to the Hi-Def NES mainboard, so if you pull those pads, it doesn't matter. Pin 19 of the PPU goes to pin 33 of the CPU, so you may need to run a patch wire.