Yes, a clear seal coat is applied to the playfield on all sides prior to any printing. That is the problem with all these playfields where the art is coming up. The digitally applied ink is adhering to the seal coat, but the seal coat is not bonding well to the wood (understatement). I know in the past, a clear polyester layer was added to the wood first, and then lightly sanded to remove any pimples and make the seal coat layer smooth. This is an inter-adhesion problem with between the wood board and the seal coat. The soft top layer clear coat is a separate issue.

I am 100% sure. A sealer coat is always applied to the playfield before printing. The issue is what seal coat is being used. It is a critical part of the process. The chemistry and application, needs to be correct and compatible with wood and digital inks.

Trying to set the record straight...

Mirco does not make Stern playfields. Mirco makes for his own repro business and JJP.

Stern makes their boards in house now, and installs the inserts, and sands the boards. I am not sure if they perform the seal coat, but I think they send them to an automotive coater in Crystal Lake, IL, who seals them, then they are sent to Rockford Silk Screen Process for digital printing,and then to the same clearcoater. Not sure, if they still use them for playfields too, but Stern once used The Fun Company in New Lisbon, WI. I know they were, maybe still are, making the wood cabinets for Stern, and possibly playfields.

American Pinball once used Mirco for the beginning of Houdini, but switched to Bader in Scales Mound, IL and then they are sent to Signcraft Screenprint in Galena, IL.

Charlie at Spooky once worked for Signcraft. Charlie gained knowledge in digitally printing playfields, etc... and has a JV with Tim Lutz at Lutz Mfg, in Benton, Wi, which is where he gets his playfields.

That is all!

Yes, the old B/W wood supplier still exists. Techniply in Oconto Falls, WI. They make the Engineered Birch and Ash 7-Ply Deck boards in Michigan.
https://www.techniply.com/specialty-plywood-1 . This is the same company Williams used, and is who Spooky uses. CGC gets their boards imported from Russia, if I am not mistaken, and am not sure about AP. They may get theirs from Techniply too! Mirco brings the wood from Canada to Europe and has it milled for the 11-Ply boards he uses in his process. The veneer ends up being thinner than the veneer in the 7-Ply boards. I have no idea where Stern gets theirs, but these boards are really not that expensive in the whole scheme of things. Why deviate from the high quality known boards for literally, a few dollars?

Techniply - Oconto Falls, Wi is the plywood manufacturer. They used to make the plywood 7 ply boards for Williams too. https://www.techniply.com/
Their hardwood veneer and process of cross laminating all the layers is exceptional. I am sure they have a lesser grade product, but the uncut board is not that expensive. It wouldn't even make sense to degrade to a lesser product for a minimal savings.

The manufacturers wish they only cost $1000 - $1500 to build. That number is so far off. Our BOM at Williams in the 90s was $2000. Labor was $250, and you had all the tooling, and development costs -- Design, Programming, Sound, Art, etc. The games were being sold for low $3000 - $3500 range. Fortunately, in our hay-day, we were making 70K games annually. The margins are not near as profitable as you think. Decent volume, low overhead, and/or cost cutting measures is the difference between losing or making money in pinball.

I agree, using the better or best playfield stock available, doesn't cost that much more. Why get all the flack for such a small incremental difference? Our raw board stock at Williams was from Techniply in Green Bay and Michigan. Not sure about Stern, but many of the other manufacturers use the Techniply 7 Ply board. Not JJP, and I don't believe CGC, but the others.

By the way, you are still low on the BOM cost for many of today's manufacturers. Pinball gross margins are fairly low. They are not keystoning the price. Stern probably comes closest.