Evolution of the separation between the two MBHs for the two merging disc galaxies setup without (top-left) and with (top-right) MBH accretion and feedback at 100 pc resolution. Ten runs with different star-formation random seeds in the galaxy are performed at each resolution to demonstrate the effect of stochasticity in the galactic environment on the MBHB orbital decay. The vertical dotted lines indicate when the MBHB evolution is handed over to RAMCOAL from RAMSES at the boundary of the resolution sphere. The black dots indicate the transition from stage 1 to stage 2 in RAMCOAL. Middle panels: time evolution of DF from gas and collisionless particles: stars and dark matter. Bottom panels: acceleration, df/dt, due to three physical mechanisms dominating stage 2 evolution: stellar scattering, viscous torque in circumbinary disc, and GW emission for all ten runs of simulation M1q0.5fg0.1 at 100 pc resolution without (left) and with (right) accretion and feedback.