Why screen scrolls up & down, auto typing etc.

In Feb 2015, I changed the charging port/board. Recently my notebook is reacting different. Soon I start working, mails in Gmail App / any application keep scrolling up & down on its own. I will be waiting for a new mail to load but random mails will be ticked, marked read, selected or again it will automatically scroll up & down to make me loose my patience.

If I try to do some browsing using chrome or compose a new mail in Gmail App, it automatically starts typing junk - specifically letters 'd' 'e' '3' "space" etc. viz. "deedd deed fde dedd 3eee d dde". I am unable to control the auto typing. Not sure where the problem is.

I tried to operate with & without the scratch guard film (originally supplied by samsung) but the screen does not respond to my finger. But the auto scrolling is controlled when styles pen touches the screen. When pen is taken away, scrolling problem starts again.

Pls suggest how to rectify this issue & what would have caused this error.