The phantom-category conjecture for degenerations of quadric bundles

Consider a degeneration of a generic quadric bundle over a surface. Let $D^b(-)$ denote the bounded derived category, and let a phantom category mean a nontrivial category with trivial $K^0$ group.

Quadric-bundle phantom-category conjecture. The semiorthogonal decomposition of the derived category of such a degeneration contains a phantom category.

The conjecture is presented as a mechanism for producing phantom categories through degeneration and is linked in the source to nonrationality questions for quadric bundles.