I almost quit making bamboo backed bows after getting 2 different bundles of of 25 slats from, Frank's. I Every bow I made from bundle #1 had a bamboo failure. Being a slow learner I ordered another bundle. This bundle arrived water logged and every slat covered with a thick coating of mold, this bundle went to the burn pile. No more Frank's bamboo for me!
Got a piece from Yumi bows, must have been green because it cracked all down the back when I put it in my drying box for a few days before a glue-up.
I get my bamboo locally now, great stuff and I have never had a failure from it. Made about 30 bows from this bamboo so far.