Panel a: fraction of cells inside the mesh where η_A (red) and η_O(blue) are being modified to prevent the MHD timestep from becoming too small, as a function of time. The dashed black line shows the evolution of the central density. Panel b: number of cells per AMR level (grey) and the number of cells where the ambipolar (red) and ohmic (blue hatched) diffusion timestep floor is operating, at a time of 28.2 kyr. Panel c: relative difference in 2D histograms of magnetic field strength as a function of density for all the cells in a simulation with Δt flooring and a second simulation without, at t = 28.2 kyr. The colour scale is analogous to that of Fig. A.1. Panel d: same as panel c but in the case of the ambipolar (red-blue) and ohmic (green-brown) resistivities.