If your bamboo is not dry when you glue it on your slat, it will tend to crack once it does dry. Once it's glued in position, it cant move as a whole, so it cracks.
Bamboo is like hickory, in that it sucks up moisture. It has to be real dry before you use it. It also changes shape quite a bit when dried. If you flatten a piece of damp bamboo, once it gets dry enough to use, it won't be flat anymore. It will have cupped towards the back, making the flattened side convex.