That is odd as the both of your components are RRS and are designed with anti-rotation keys. There are several options, welding the parts together, or using epoxy. Filling the b2-40 pockets with JB weld and then tapping or pinning additional connections, or even fabricating a better interlocking pic rail. One might also remove the pic rail clamp from the bipod and look at fabricating a direct mount to the B2-40. Anyhow I would contact RRS for a solution. The point of their design is to key the parts together to prevent the problem you are describing.
Rasyad