Bragg structures with distortion of periodicity are considered. Effects of scattering the wave beams falling at oblique angles are theoretically investigated. Methods of characteristic matrices and plane-wave decomposition are used for obtaining angular and spatial distribution of reflected and transmitted wave beams. Magnitudes and phases of scattered fields are analyzed. Phenomena of anomalous behavior of group shifts (decreasing and negative ones) are observed for Bragg structures with different type of periodicity distortions.