[Q] HTC One top touchscreen problem - Bug or Hardware fault?

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http://forum.xda-developers.com – Hey, I have an HTC One black - stock os - UK unlocked version - after 4.2.2 update. I've got a strange problem regarding the top of the touchscreen. when the phone is horizontal, the top bit (between the top bar to the first widget) is not working. the rest of the screen working fine. when I pick the device up, the screen is working fine 70% of the time. as a result, I cant open the notification bar and it thinks that I'm clicking or re-arranging my widgets. 1. did any of you experienced any of this before? 2. What do you think it is? software or I have to replace the digitizer? (HowTos)