I'm trying to think of a game that I've had where the board isn't flat...Field Commander: Alexander I had issues with. I want to say I have another but to be honest I can't remember what it is or if it even exists in my basement. Overall made in China, Germany or US I haven't had issues.
Avalon Hill's Robin Hood, but that's more an issue of panel size than the boards warping.
I wouldnt give hasbro too much credit for flawless boards.
My copy of Waterdeep was one of the worst warped things ever, besides the hasbro Betrayal.
FFG products seem to be pretty hit or miss for me. It's always a gamble. But I guess replacing items instead of finding a producer to manufacture it right the first time is cheaper to do.
I really miss the days of Rio Grande. It was always so nice to open and punch a european printed game. Tiles fall out of frames with no sprue tufts, boards are well printed on quality stock. Its a shame I dont like more of those games, as they seem like heirlooms compared to a lot of crappy quality we see nowadays.