Part of touch screen is not working
I might be late, or maybe not. I confirmed (here) this issue being adressed into a firmware where the asigned screen size was bigger than it was supposed to be. In my case, a 7" tablet flashed with a 10" screen size tablet, downloaded straight from the tablet's company support page, for my specific tablet.

The guy from the link applied a solution by himself, using pieces from another firmware so the screen size matched the desired one. You can either do this or try another firmware, if it exists.