Here we go with these treads again. There must be dozens by now proclaiming that this issue has been fixed over the months and it always proves not to be. This will not be be fixed. It's a hardware problem.
No, it's not a hardware problem. My tap issue was fixed permanently with both DP 8.1, and Cyan.
Why would it be a hardware problem? It's more likely to do with firmware - in particular my theory is to do with processing threads, as the problem always became more frequent on certain intensive apps, but was a lot milder on the OS.
Plus if it were a hardware problem, how come me and a few others have had the problem fixed through updates? It was a display or glance update that fixed it for me last time and in the entire time I used DP, and the entire time I used cyan, I haven't had the tap problem. However when I downgraded to 8.0 before Cyan, the problem came back. Then I got Cyan and it went away again.
I think the problem lies in the way the phone talks to the hardware, evidenced by the fact that when the issue doesn't occur the touchscreen works just fine; and the issue isn't always occurring in the exact same spot every time.