Tap 10.1 Verizon extremely unstable 5.1.1

[thematrixz]

This is a 2014 10.1 version, Verizon. Since I updated to 5.1.1, the tablet has been so unstable to the point I hate to use it.

1. Screen refreshes itself: every few seconds, the screen would refresh itself (on the desktop, I can see the screen flickers when it refreshes), in Facebook, the feed updates itself making it's hard to keep tab on where you were.

2. Video issues: this might be related to problem 1, if I was watching a video, it might restart at the beginner only after a few seconds, and this process will keep repeating itself for a while, sometimes, it will play for a a few minutes before restarting.

3. Kodi either crashes or freezes after a few minutes of usage.

I have tried a few suggestions found on the web: ie. changing Animation to 0.5 instead of 1, turning off video overlay acceleration without any positive result.
I have also tried the obvious like doing a factory reset, clear the cache partition,..... nothing worked.

Please help, I'm just about the throw this thing out the window or finding a way to downgrade it back to Android 4.4.x

Thanks

Tan