Matlab fminsearch get's stuck in first iteration - matlab

Question

I'm doing an optimization on a simulated robot's walk with the fminsearch method. What I did is create a function (the objective function) that writes to a text file the walking parameters (the input of fminsearch), opens the simulator (in webots) which writes the result of the walk in a text file and closes itself and then the objective returns the value in that text file. To sum up- the objective function get's a 8x12 matrix of leg position's and returns a scalar which indicates how good the walk is.
This works and the position values really change each iteration and the objective value improved indeed.
But here is the problem- I want to follow the function's value in each iteration (preferably by plot) and when I do that I get only the function's value at the first iteration and I can't understand why.
Here's the code:
options= optimset( 'PlotFcns', #optimplotfval);
[position,fval] = fminsearch(#callWebots,pos_start,options);
I tried displaying the results too and the same problem occurred (it displayed only the first iteration):
options= optimset(options, 'Display', 'iter-detailed');
I even tried to write an output function which will plot the fval and occurred with the same problem.
I would be grateful if you have any ideas why this can be...
Thank you in advanced
Here's the objective function:
function [objFun]=callWebots(pos)
%Open Motion File
filePath= fullfile('C:\Users\student\Documents\Webots\worlds', 'motion_trot_opt.motion');
data=convertToData(pos,filePath);
fout=fopen(filePath,'w');
%Write Motion File
for row=1:size(data,1)
for col=1:size(data,2)
if(col>1)
fprintf(fout, ',');
end
fprintf(fout, '%s', data{row,col});
end
fprintf(fout,'\n');
end
fclose(fout);
system('C:\Users\student\Documents\Webots\worlds\robot_full_withGPSLighter.wbt');
% Get result and return to main function
resfilePath= fullfile('C:\Users\student\Documents\Webots\worlds', 'result.txt');
fres=fopen(resfilePath);
result = textscan(fres, '%f');
fclose(fres);
objFun=cell2mat(result);
And the call for the objective function:
function [position,fval]=optCall()
%Read Initial Motion File Into CELL
filePath= fullfile('C:\Users\student\Documents\Webots\worlds', 'motion_trot_opt.motion');
fin=fopen(filePath);
ii = 1;
while 1
tline = fgetl(fin);
if (tline == -1)
break;
end
SplitedRow(ii,:) = regexp(tline, ',', 'split');
ii = ii+1;
end
fclose(fin);
%Convert from double to Data
[n,m] = size(SplitedRow);
pos_start = cellfun(#str2double,SplitedRow(2:end,3:end));
options= optimset( 'PlotFcns', #optimplotfval);
options= optimset(options, 'Display', 'iter-detailed');
[position,fval] = fminsearch(#callWebots,pos_start,options);