[Q] Part of screen doesn't work (ST15i) topic

I have sony xperia ST15i and parts of my screen doesn't work (Please see attached image, parts that are colored red are not working).
So my question is: How can I fix this?
I tried using some apps for screen recalibration and I tried reflashing stock firmware and nothing seems to help.
Do I need to take it apart and clean the contacts or do I need to change touch screen?

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