Cubic Pm-3n Nb3Sn0.92 superconductor (Tc ~ 16 K) was found to exhibit tetragonal instabilities at the superconducting state (T = 10 K). These are manifested through appearance of reflections which forbidden in symmetry but compatible with P42/mmc structure is observed Nb3Sn1-x system for higher Sn content temperatures lower than 43 K. Nevertheless, low-temperature remains metrically fully cubic...