I recently bought some walnut for some lams.Got them all cut and ground, they looked pretty good. Grain was nice, gave them a flex test and had all of them explode on one end, almost looked like they were dry rotted??? Kind of similar checking to what yours looks like.Do you have any left over wood that you could test . Talked to a couple of people about it because the wood did not look bad. One of them thought it might been salvaged from a river?? Anyone familiar with this?? I would be careful with it, if you hear any funny clicks coming from it I would beware.