I have a Next3 also and I am getting the same android.process.acore error, also sometimes I get two other errors:
com.google.process.gapps
process bn.ereader
i have tried everything, resetting the device, etc. Nothing works. I left a message to tech support today, so maybe they will let me know something. If they do I will post it here so you can fix your problem too. And if you find a way to fix it, post it here so I can fix mine also.
I think we need to do a factory reset, but because of the error we can't get access to the settings area. The device is totally locked except for being able to click on "Force Close".
My Next3 has been working great for over two months. I know last night I removed some apps, some of which I think were attached to the OS, andn that is what created my problem. I am using my Next3 just as it came from Nextbook, no rooting. I think I deleted something important when I was deleting things last night.
Let's hope we can find a quick answer to the problem. I was hoping to take my Next3 on vacation next week.
Keep in touch.