Will you look at this:
http://forum-rc-warships.xooit.eu/t26-Mon-Yamato-au-1-150.htm?q=graupner+yamatoIt's a French site but scroll to the end and have a look at the decking!
Grrrr Graupner have known of this problem since they launched this Premium range. The poster had it exchanged by Graupner and the new one had the exact same problem.
I had the same problem with the veneer deck on the very first warship they released in the range- the Prinz Eugen and then the Sharnhorst and that was years ago. This Yamato was only released last year! Such an expensive model and they use this horrid stuff for the deck still and don't get me started on all those fragile anti-aircraft gun barrels made from resin....
Its a great pity because they give someone who does not have the time/skill to build something like this a chance to own the ship of their dreams. I kind of solved the problem on my ships by using a hair-drier on the veneer then trying to seal the deck edges and coating it in Ronseal- but can still warp from time to time.