This is a problem, because it shows that the pure spinor formalism in the form described in (N.Berkovits, P.Howe) does not correctly reproduce the supergravity states.

These states are removed by the Virasoro constraints , as we now explain.

Still, there is something I dont understand here, because according to the paper of N.Berkovits and P.Howe, the BRST cohomology should be enough.