Brass scale liner goof up

I've got some interesting white oak "crotch" that I wanted to try to make into scales. When I received them they where flat but after a few days sitting unbundled they warped like this:

Attachment 157263

I steamed them for a half our then clamped them between two pieces of hardwood flooring for two days and they came out straight:

Attachment 157264

I then sanded out all the saw marks and glued them to thoroughly sanded .01 brass (I cut it with a paper cutter) with Gorilla Glue and placed them between the hardwood again with a little weight on top. They came out nice and flat like this after sitting over night:

Attachment 157265

I had cut the brass a little wider than needed and it ground down nicely.
I set it aside for a day and was left with this:

Attachment 157268

You can see the crack in the one I tried to flatten out. At least I know there is a good bond. I think they warped because I dampened them to see the grain to be sure I had the book matched sides oriented correctly and then a little more moisture when I applied the glue because the instructions said it needs moisture to cure. Too much moisture for sure, probably should not have used any as I think the wood expanded before gluing and then later dried and contracted curving because the brass stayed the same size and the wood could not pull away.

Any observations are welcome.

Looks like when the wood finished drying it shrunk down and since the glue held it to the brass there wasn't anywhere it could go, but to curl on itself to release the tension. Burl woods have a tendency to be fragile when not stabilized. I am not that familiar with drying and curing of wood so my 2 cents is all speculation. I am actually looking forward to what others have to say.