Comment (by Samuel Cupp):

To have more correct scheduling, change the in HydroBase_Con2Prim to in HydroBase_PostStep after HydroBase_Con2Prim.
This is because that con2prim group also runs in PostPostInitial where IllinoisGRMHD manually schedules functions. This should only put it in the places where AddToTmunu appears. I still get nans, but I don’t have time right now to track down where they come from. If you track down where they first appear, please let me know.

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Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2497/illinoisgrmhd-is-incompatible-with-setting