load_minus_flux_data in 3D grid size mismatch or kernel crash

[Olav-Schiess]

When subtracting the flux data from my sim1 in my sim2 using load_minus_flux_data in my 3D transmission simulation I get the RuntimeError: meep: grid size mismatch 12800 vs 43808 in fields::load. How can I prevent this?

Following the same structure as the example from Transmittance Spectrum of a Waveguide Bend:
I run sim1 without the geometrical feature. Save the flux in reflected and transmitted region. Then setup sim2 with the geometrical feature and subtract the field from sim 1. This is where the I get my errors.

I've tried most things from Load and Dump Simulation State without luck.

Here's a snippet of the code. For this code the kernel dies.
sim1 = mp.Simulation(cell_size=cell,
boundary_layers=pml_layers,
geometry=[],
k_point=mp.Vector3(0,0,0),
sources=sources,
resolution=resolution,
subpixel_tol=1e-5,
symmetries=symmetries,
# split_chunks_evenly=False,
)

refl_fr = mp.FluxRegion(center=mp.Vector3(0, 0, -0.5 * sz + dpml2),
size=mp.Vector3(sx, sy, 0)) # Region to measure reflected flux
tran_fr = mp.FluxRegion(center=mp.Vector3(0, 0, 0.5 * sz - dpml2),
size=mp.Vector3(sx, sy, 0)) # Region to measure transmitted flux

refl = sim1.add_flux(fcen, df, nfreq, refl_fr)
tran = sim1.add_flux(fcen, df, nfreq, tran_fr)

pt = mp.Vector3(0, 0, sz / 2 - 2 * dpml) # A point in the transmission region
sim1.run(until_after_sources=mp.stop_when_fields_decayed(20, mp.Ex, pt, 1e-2))

nogeom_refl_data = sim1.get_flux_data(refl)
nogeom_tran_flux = mp.get_fluxes(tran) # Transmitted flux

sim1.dump_structure(fname='sim_structure.h5', single_parallel_file=True)

sim2 = mp.Simulation(cell_size=cell,
boundary_layers=pml_layers,
geometry=geometry,
k_point=mp.Vector3(),
sources=sources,
resolution=resolution,
# split_chunks_evenly=False, # Control chunk distribution
# chunk_layout=sim1,
)
sim2.init_sim()
sim2.load_structure(fname='sim_structure.h5', single_parallel_file=True)
sim2.k_point = mp.Vector3(0, 0, 0)

refl2 = sim2.add_flux(fcen, df, nfreq, refl_fr)
tran2 = sim2.add_flux(fcen, df, nfreq, tran_fr)

sim2.load_minus_flux_data(refl2, nogeom_refl_data)

Here's a 2D plot of sim1 and sim2 in the XZ plane

[Olav-Schiess]

I don't know what the issue was yesterday for me to add load and dump but It runs fine without these lines of code. Also I needed to add symmetry to sim2.