I bought the original Nexus 7 the day it came out in 2012 and since it has had an annoying screen flicker issue which is most visible on white backgrounds like surfing the web. I have put up with this for over a year but finally got annoyed enough to see if there was a way to fix it. I searched the web but did not find a solution to this issue. I tried a bunch of stuff like tweaking Wi-Fi settings, setting the backlight to a constant brightness, and using root only backlight control program all will no luck. It seems to be an EMI issue that stems from the Wi-Fi connection, if I turn off Wi-Fi the issue resolved itself but that makes the tablet pretty useless for my needs. So I popped the back cover to see if I could shield the board from the Wi-Fi antenna. I have been able to resolve the issue and here is a basic rundown of how to fix the issue.
The circled Wi-Fi contacts connect to a Wi-Fi antenna on the back cover of the device. The goal is the shield the PCB directly below this antenna to block it from radiant EMI.
I insulated parts of the board that could make electrical contact with the shield using Kapton tape.
I was out of copper tape so I used aluminum foil, not the greatest thing but it works. Make sure you tape the shield to the metal shields on the top of the PCB to make electrical contact and ground the shield. The downside to this modification is it reduces your Wi-Fi signal strength but was something I was willing to trade to get rid of the flicker.
This is not my video but demonstrated the screen flicker issue to those who do not have it.