Recent experimental data on dijet cross sections in diffractive photoproduction at HERA collider were analysed with emphasis on QCD factorisation breaking effects. Dijet photoproduction data of jets with low transverse energy E T1 > 5 GeV indicated a possible dependence on E T of the suppression of jet production with respect to the NLO QCD predictions. However, this suppression exhibited no significant dependence on the fraction x γ of the photon four-momentum entering the hard process. The ratio of diffractive to inclusive cross section for dijets in photoproduction was also measured for the first time.