My WOZ has a 12/15 build date. It has the 7.5V or 7.5V buffered light boards. I'm not sure. I bought my WOZ with less than 100 plays and it had a bad light board when I got it (I knew this going into it). JJP sent me a replacement which also failed a few plays after installing it. They sent me a second replacement and the machine has been problem free for 1 year now, 1148 plays, and 31 days run time. Take that to mean what you will but I've been happy with the machine's reliability and JJP support.
(One thing that doesn't get brought up enough when the light board issues are discussed is possible cable issues. They seem to carry ground via the shield rather than a wire. They solder a small wire to the shield to make the connection right before the connector. I found that this wire was broken on my cable going into the failed board. I suspect this is why the first board they sent me failed and perhaps why the original board failed as well. I fixed this before installing the second board they sent me and I've had no issues).