Laptop keyboard malfunctioning?

You cognise however you hold down the "down" key and it scrolls down on a page? mine meet suddenly cease doing that.. i command down "down" key and it only scrolls like 1cm (you know what i expect).. and as i was writing, it would miss out letters if i were to type"qwertyuiop" normally, it would type "qwtyp".. something like that.. did a restart and problem was gone.. why did that happen you bet can i prevent it? or is it instance to do a refund / return/ trade off? this is the 1st time it happened.. thanks
LAPTOP: HP PROBOOK 4530s