you have got faulty touch interface, big metal square on screen flex. It should be replacement. Many times, “small, Chinese hands” when assembly a big, 12.9” screens use a used interfaces and flexes for new product. Most of those are re-soldered from broken and flooded ones and normally not working properly. Inspect your screen, I guess - there are lots of fingers signs and small, blue stamps? Everywhere? This is a reason why most brand new screens are with no touch interface - it needs to be transferred from your original, broken one - that’s a guarantee full compatibility.
how to solve the problem: the first choice: I thing, you should send back this “brand new” screen (if possible: transport foil is on it or replace with a new one more time) and find other best offer. Somewhere was a guy, in LA who refurbish a tablets screens. His work is much better than Chinese, new screens. Find him on eBay. The second choice is a buy a brand new touch interface with the flex for your model (circa 20$) and solder it to your “new”screen. I’m afraid there is no other options.
I assume the situation that the new screen is properly connected and there is no situation that you put the whole thing together wrongly. Check it before: disconnect the battery, detach the new screen, insert it again, making sure the connection is ok. Connect the battery and check the touch. Be very gentle, it is easy to destroy the contacts. You should hear a click when the connector finds its own place.
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