Macbook Pro trackpad gets stuck and screen freezes with pink and yellow lines
So I'm really frustrated. I got my Macbook pro less than a year ago and Ive already had to get a bunch of parts replaced. I got my computer repaired like 3-4 weeks ago and they had to replace a lot of things ( don't remember what it was, but they had to disassemble the entire computer and replace some things that were related to the battery/power). Recently my computer has been doing this weird thing where the screen will freeze and pixelated pink and yellow lines will just take over the screen. In addition to this, the trackpad will just get stuck and I have to shut down my computer and turn it back on in order for everything to function. Has anyone heard of anything like this? I was thinking that maybe when I got my computer repaired they didn't replace everything properly? I did a hardware check on my computer (that self-checking one Apple recommends before scheduling an appointment at the Genius Bar) and it said that everything looked fine. Is this sounding like a hardware issue? Could it be a virus? Someone hacking into my computer? I don't know, I'm just worried and frustrated :/
Thanks!
MacBook Pro (13-inch Mid 2012), iOS 9.3