Hi Ian,
Have you seen this video ?
https://www.youtube.com/watch?v=ImigoFK-ZeU
It's all about a backlight problem but could be helpful.
Concerning your own lcd issue I would bet on a contact issue between the ribbon cable and one of the boards. Check for cold/loose solder. The ribbon cable itself might be faulty, if you have a multimeter you can check continuity. Twisting the ribbon cable might cut one of the wire.
You can also ask access/kemper for the lcd board reference, maybe they have some spare or you might source one by yourself in online electronic shops.
http://www.gravitech.us/16chbllcdwib.html
I reckon this kind of lcd could be compatible since there are 16 soldering pads like yours.
Hope this helps & keep us posted
Frederic.