Firstly I would check for a vcc main short. It most likely will have one. How you track it down depends on what tools you have. Freeze spray, flir cam or the old fashioned way with your tongue. Update (05/16/2019): C4127 would be the best to check vcc main.
It sounds like the wifi chip might need replacing. You might be able to find a repair shop to do it. But it won’t be cheap as they will also have to remove the nand and write the new wifi serial number to it.