Abstract The vertical motion and shrinking of the cold plasma column after a tokamak disruption leads to a natural decrease in the edge safety factor when all the current is carried by runaway electrons. Reaching a low edge safety factor can potentially cause a strong plasma instability. We present magnetohydrodynamic simulations of the termination of a post-disruption plateau-phase runaway electron beam in ITER when the edge safety factor falls close to two. Growth of instabilities is observed to result in stochastization of the magnetic field and a prompt loss of runaway electrons. Higher background plasma resistivity is seen to cause larger mode magnitudes and stronger stochastization, leading to less remnant runaway electrons after the termination event. Lower ion-densities also project a qualitatively similar behaviour although weaker in effect. Using computations from a wall collision model, the ensuing load distribution on the first-wall is also presented.