New LCD panel colored lines

Hey all,

We just replaced a cracked iPhone with a new LCD screen. The screen works for about a minute, then colored lines show up and it goes black. Hitting the top button twice turns the screen back on (for another minute or so). We thought maybe it was a faulty product, except we re-connected the cracked screen and the same thing started happening. We've tried resetting the phone. We've done research and we didn't put the screws in wrong. Wondering if its the ribbon cable? Or something else.

Thanks in advance