Master System - Master help needed for lines issue

I picked up a Master System with cables and controllers the other day, knowing it had this issue. It was pretty cheap, so I went for it. Anyway, some lines of pixels are missing or just mis colored. Does anyone have any ideas what this could be? Im gonna open it up later and dust it out pretty good, and clean out the cart connectors. Also, it does this with or without a cart in. Here are some pics.









Notice the heavy black bars in the corner? Those dissapear after the the maze has transitioned to the center of the screen. Thanks in advance for any help.

 

open it up and check for any signs of damage or leaking caps, dry solder joints n the like, has someone screwed with the bios?

 

Ill give it a good looking over tonight. Hopefully it's something relatively easy to fix.

 

So I looked over everything a couple of times, dusted it, cleaned it, but still get the weird lines.