There was a revision that moved the contents of the daughter board to the main board. Also, the buttons which were about 1/2 inch tall, were extended to two or three times as big, so they could reach to the main board. I don't know the exact dimensions of the buttons, so don't worry about correcting me.
I think the problem was the type of solder that was used. So I suspect if you could remove and replace the solder, things would work better. I have many that have bad displays, and many that I've fixed.