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Letter " N " not coming onto screen. When "N" is pressed there is a space in sentence.
Maybe you're tapping somewhere else than you think you do.
Nice experiment:
Open settings
Search for build number (System->about phone)
Tap on build number several times and developer options appear as a new menu
Inside developer options scroll down to show taps, switch it on and after that you can see where exactly you are tapping.
If that isn't clear enough you can switch on pointer location as well.