[Help] Returning to stock

Hi,

I have a recalled shield tablet that has been flashed with latest twrp and bliss 6.4 nightly 06.22
I notice a static noise in the speakers most of the time, louder when i touch the display.
Also it is high on battery usage.

I want to return to stock but i am unsure of the best method.
I would like to keep twrp if possible, i have read the guide on the nvidia site and i am ready to do it that way if no other way exist.

So can i just flash the stock img file in twrp? or do i have to restore it fully to stock and then reinstall twrp and root?
do i need to flash both of the larger img files in the stock package?

Would be nice with some help.

Thanks.

from xda-developers http://ift.tt/292pKpe
via IFTTT