White lines on the left side of the screen after replacement

Hello; I've replaced my cracked screen on my iTouch 4gen, following the instructions provided here on the iFixit; the problem is that once I started first my iPod, two white lines appeared on the left of the screen... everything else looks fine (for now); I didn't glue the screen at first, so I can go backwards if anything goes wrong; I've tried re-seating the display cable, and looked for cracks on the ribbon cable and looks ok! ... I've tried already a hard reset with no luck; now I have turned it off and I'm writing this post to see if this have happened to anyone before; any ideas?