The Bragg glass phase and its transition into the disordered vortex state at high fields are investigated by magnetization measurements in V₃Si varying nucleation and annealing of metastable disorder in a distinct manner. The extension of the Bragg glass becomes reduced by disorder from edge contamination and by frozen disordered phase. The relevance of these effects and their mutual interference depend on the lifetime of the metastable disorder and the time scale of the measurement. Magnetization loops, sequences of minor loops, and the transient decay of the irreversible moment are investigated by varying the sweep rate of the applied magnetic field and vortex shaking from the vibration amplitude of the magnetometer. Deviations from the standard Bean model based on a homogeneous flux distribution are used to separate frozen disorder, edge contamination, and Bean critical current in the Bragg glass phase. A comparison with YBa₂Cu₃O₇ demonstrates the common nature of these contributions to the magnetic moment and the importance to identify them for the correct interpretation of vortex phase diagrams.