HADES is a large acceptance spectrometer operating at SIS18, GSI, in Darmstadt, Germany 1. It is aimed at exploration of the QCD phase diagram at the ion beam energies of 1-2 AGeV in the region of high density baryonic matter. An unphysical behavior of particle directed flow deduced from raw experimental data obtained during experimental study of Au+Au collisions at 1.23 AGeV is observed. It is found that dependence of the directed flow on rapidity does not show the antisymmetry expected in the symmetric projectile-target system, and there is significant non-zero directed flow at midrapidity where this component has to be zero, again from the system symmetry reasons. Possible explanation of the effect is due to the final granularity of corresponding detector and hence limited resolution of close particle tracks.