I made an end grain cutting board out of 8/4 walnut and quartersawn red oak. It clamped up beautifully with moderate pressure and I planed it dead flat.
Now it is bowed about 1/4" and is barely usable. It has not been submerged.
I finished it with 2 coats of mineral oil and 1 coat of mineral oil with 25% beeswax.
Any thoughts about this thing being unstable?