Runaway electrons can enter strong mutual interactions with MHD modes. Our main goal is to use the RE fluid model of JOREK to investigate benign RE beam termination in JET. Previous simulations [1] had taken particular assumptions regarding the properties of the background plasma, e.g., regarding the resistivity, that might not be accurate due to the recombination following massive deuterium injection. Moreover, these simulations have considered a highly MHD-unstable situation that leads to fast RE losses. Thus, we have repeated these simulations with several sets of different assumptions regarding the accompanying plasma conditions, and the results of this work are presented here. Along with that, the first steps towards the transition into the highly MHD-unstable situation are also shown. [1] Bandaru V., Hoelzl M., Reux C., et al. Magnetohydrodynamic simulations of runaway electron beam termination in JET. Plasma Physics and Controlled Fusion 63, 035024 (2021)