  We calculate diffractive dijet production in deep-inelastic scattering at
next-to-leading order of perturbative QCD, including contributions from direct
and resolved photons, and compare our predictions to preliminary data from the
H1 collaboration at HERA. We study how the cross section depends on the
factorization scheme and scale M_\gamma at the virtual photon vertex for the
occurrence of factorization breaking. The strong M_\gamma-dependence, which is
present when only the resolved cross section is suppressed, is tamed by
introducing the suppression also into the initial-state NLO correction of the
direct part.
