lsqnonlin() with Simulink

I am using lsqnonlin() with Simulink as it is used here. I am getting the errors:

1. Unable to perform assignment because the size of the left side is 30012-by-1 and the size of the right side is 30018-by-1
2. Error in finitedifferences
3. Error in computeFinDiffGradAndJac

Here is my code:

function [f] = trackq

% Computes f using lsqnonlin.

mdl = 'armDynamics';

open_system(mdl) % Load the model

in = Simulink.SimulationInput(mdl); % Create simulation input object

in = in.setModelParameter('StopTime','100'); % Stop time 100

f0 = 1; % Initial f

%

options = optimoptions(@lsqnonlin, 'Algorithm', 'levenberg-marquardt',...

'Display','off','StepTolerance',0.001,'OptimalityTolerance',0.001);

% Optimize f

set_param(mdl,'FastRestart','on'); % Fast restart

% f = lsqnonlin(@compute_error, f0, [], [], options);

f = lsqnonlin(@compute_error, f0, [], [], options);

set_param(mdl,'FastRestart','off');

function error = compute_error(f)

% Set the simulation input object parameters

in = in.setVariable('f', f, 'Workspace', mdl);

% Simulate

out = sim(in);

% get q from the actual space arm

armCoords = out.qArm.signals.values;

armCoords = armCoords(2:4);

armCoords = armCoords';

% get q from modelled space arm

qsim = out.get('yout');

qsim = qsim.getElement(1);

qsim = qsim.Values;

qsim = qsim.Data;

qsim = qsim';

error = armCoords - qsim;

end

end