Array-dimension of sensitivities does not match with variing t_eval steps

[tGisbertz]

Hello all,

I want to calculate the sensitivities of some parameters with the DFN model. I used this notebook (2021-09-workshop/Session 3/sensitivities_and_data_fitting.ipynb) as a baseline and added a parameter set, geometry, different input parameter and also changed t_eval.
Now I get this error: ValueError: x and y must have same first dimension, but have shapes (500,) and (494, 1).
When I change t_eval to np.linspace(0, 3600, 1000), I get this error: x and y must have same first dimension, but have shapes (1000,) and (988, 1).
With the default steps of 100 I get the error: ValueError: x and y must have same first dimension, but have shapes (100,) and (99, 1)

Is there something I'm missing so that the outputs have matching dimensions?

This is my code:

import pybamm
import numpy as np
import matplotlib.pylab as plt


# load model
model = pybamm.lithium_ion.DFN()
# create geometry
geometry = pybamm.battery_geometry(form_factor="cylindrical")

# load parameter values and process model and geometry
param = pybamm.ParameterValues("Chen2020")

param.update({'Positive particle radius [m]': "[input]"})

param.process_geometry(geometry)
param.process_model(model)

# set mesh
var = pybamm.standard_spatial_vars
var_pts = {var.x_n: 30, var.x_s: 30, var.x_p: 30, var.r_n: 40, var.r_p: 40}
mesh = pybamm.Mesh(geometry, model.default_submesh_types, var_pts)

# discretise model
disc = pybamm.Discretisation(mesh, model.default_spatial_methods)
disc.process_model(model)

# create solver
t_eval = np.linspace(0, 3600, 500)
solver = pybamm.CasadiSolver(mode="safe", atol=1e-6, rtol=1e-4, max_step_decrease_count=20)

# evaluate the senstivities
solution = solver.solve(
    model, t_eval,
    inputs={'Positive particle radius [m]': 5.22e-06},
    calculate_sensitivities=True
)
plt.plot(
    t_eval,
    solution["Terminal voltage [V]"]
    .sensitivities['Positive particle radius [m]']
)
plt.xlabel(r'$t$')
plt.ylabel('sensitivities of Terminal voltage wrt Positive particle radius [m]')
plt.show()