Down arrow key not working & continuous scrolling down

Hello,

I have an Acer Aspire V5-571G, and all of a sudden my laptop started scrolling down on its own. It would stop when I hit the up arrow key, but then would sometimes continue on scrolling down. Then I realized that my down arrow key was not working. Whenever I press it, nothing would happen, I pressed it a few times and the pages would budge down a little bit then drastically start scrolling down fast again non-stop.
I pressed the arrow keys a few times and when I started to type my whole keyboard was messed up. One letter key would send out two letters, the "A" key would function as the CAPS lock etc, restarting my laptop helped fix it, but the down arrow key and the continuous scrolling is still there.

I can scroll up and down well using my number pad and an external keyboard, and I just had this keyboard replaced recently...
Is it broken again? Is there another way I could fix this before I take it to the repairs and pay more?