Unknown Short To Ground From 5v Power

I recently found my old Atari Lynx. I installed the power circuit refresh kit (replaced the MOSFET, etc) and the Lynx worked, though turning it on sometimes took a few presses of the button. I did the McWill screen mod next and that went well and seemed ok, but the issue with having to press the power button a few times remained. Next I did a recap of the board, thinking the issue was due to some old/bad capacitors. It appeared to work fine after that, but a day later it refused to turn on at all. I did some testing and I believe there is a short from 5v power to ground. I undid the recap (put the old caps back) and the issue still remains. I don't see any obvious shorts, nothing wrong with any of the solder joints, etc. The only area of the board I haven't touched with the recap is under the shield under the cartridge connector. I guess I'll need to look there. In the meantime, I went back and lifted one leg of each of the caps I had worked on, but the short remains. Any advice on how to track down the short from here?