Supergravity and matrix theory do not disagree on multi-graviton   scattering
  We compare the amplitudes for the long-distance scattering of three gravitons in eleven dimensional supergravity and matrix theory at finite N. We show that the leading supergravity term arises from loop contributions to the matrix theory effective action that are not required to vanish by supersymmetry. We evaluate in detail one type of diagram---the setting sun with only massive propagators---reproducing the supergravity behavior. 
Marco Fabbrichesi, Gabriele Ferretti and Roberto Iengo