The random-field Ising model (RFIM) system Fe0.42Zn0.58F2 is studied by magnetization and dynamic susceptibility measurements, under finite dc applied fields (H). For H < 20 kOe, the magnetic behaviour is compatible with a long-range ordered (LRO) antiferromagnetic (AF) ground state, which undergoes a phase transition (PT) at a critical temperature Tc(H). For higher H, the LRO configuration becomes unstable and the PT is destroyed. A glassy dynamics emerges in the upper part of the (H,T) phase diagram. Our results reconcile earlier concepts associated with the weak RFIM problem with recent experimental data in FexZn1 − xF2.