How many decks have you bought or made that over age become twisted. The deck may have been left in the sun too long or left beside a heat source. The results of this can ruin a board.
Uneven drying of veneers is something most of us have encountered.
Here is a quick fix.
2 light duty clamps.
set of strait edges like two 12″ metal rulers.
An industrial heat gun. Home Depot, Lowe’s have them.
24″ piece of 1 x 2
Take your board and clamp one end to a table using a light duty woodworkers clamp, top side up. Take two strait edges and position them as far away as possible. One on each set of truck mounts works great. Position them as shown in the picture. I ususlly put a couple of woodworking screws into the truck holes to lean the strait edges against.
From the front of the deck eye along the tops of the strait edges. This will clearly show you how much your deck is warped.