Some routines in GRHydro query whether a point is excised using hydrobase's excision mask. HydroBase initializes the excision mask to zero in certain groups. However, this initialization should happen before any other code reads the excision mask. Since GRHydro reads the excision mask in Con2Prim, which is scheduled in MoL_PostStep, the mask should be set before MoL_PostStep!
Most notably, this is required in post_recover_variables (since the mask is not checkpointed and thus we critically rely on a correct mask initialzation), and also in post_regrid, where new points must be correctly initialized.
I attach a simple patch that fixes this issue.