It's been a long time since I used an L&M; usually no problem with that particular piece.
I can recall getting the wire pinched while closing the back - it was hard to diagnose since the outside of the wire looked OK. Also, if the other end of the wire wasn't plugged all the way in, problems...
The solder joint between the cable and the monitor (inside the back itself I think) can also cause a problem.
Here's one of my writeups that may help with diagnosis (or not!): http://wetpixel.com/...lem#entry312482
Be careful with this - it worked fine for me; you may not be as lucky.
L&M replaced the motherboard in the OLED back under warranty and all was good. Maybe yours needs that?
It couldn't be anything simple like the flip filter being in place when you wanted it out of the way, or the white balance way off and needs to be redone? You have no doubt tried these but I needed to mention them just in case.
No picture was attached to your message, so couldn't see what you were seeing.