We experimentally study polarization dependent linear and nonlinear dynamics in waveguide arrays. We found that in certain arrays, the band structure and the modal shapes of the array modes are markedly different for the two polarizations, in a manner that cannot be simply explained using the effective index approximation. Specifically, one of the gaps was found to be missing for the TM polarization. In the nonlinear regime, we observe mixed-polarization nonlinear localizations in high bands, such as Band-2 Floquet-Bloch vector solitons. The band structure anomaly enabled the excitation of a multiband moving breather.