LCD cuts out randomly, connection okay?

After repairing a cracked digi for a customers iPad 3, he brought it back in after a few months complaining that the LCD was cutting out randomly. Looking at it myself, it's exactly that - the LCD just goes to sleep at its own volition, and pressing the power or home buttons turns it back on normally. So I popped the digi off and found that the little black plastic "lock" for the LCD cable was broken off. The cable was fully seated, but I reseated it anyway, and then put some electrical tape over it. Before I closed everything up I checked it thoroughly, shaking it around and whatnot to see if I could replicate the problem; everything seemed okay so I sealed it up.

Wouldn't you know it, as soon as everything's back together, it starts going to sleep randomly again! Has anyone seen something like this before, or have any ideas?