All I can say is that the touchscreen driver is pretty messed up in general. There are multiple issues on this tablet, like shaking when you hold something, multitouch not working properly and touchinput dropping for no reason.
I'm not sure if your issue is hardware or software related (could be both imho) but I'm pretty sure the touchscreen driver will get some bugfixes in the next update. It's extremly needed and Samsung should be aware of it...
Phone: Samsung Galaxy S III | Stock rooted
Tablet: Galaxy Note 10.1 2014 Edition Wifi | Stock rooted