Script Returning NaN when it is inside a WHILE loop

So I have this MATLAB code for Newton Raphson Power flow and I need to find the answer within a tolerance limit of 1e-6. But the problem is that once I input my script inside the while loop, the output is returning NaN values. When I remove the while loop, it works...Any help will be appreciated.

% The Ybus matrix is

[yb,~]=ybusnr;

g=real(yb);b=imag(yb);

% The given parameters and initial conditions are

p=[0 0.5 -0.275 0 -0.15 -0.25];
q=[0 0 -0.11 0 -0.09 -0.15];
mv=[1.05; 1.05; 1; 1; 1; 1;];
th=[0;0;0;0;0;0];

del=1;indx=0;

% The Newton-Raphson iterations starts here
while del>1e-6
   for i=1:6
      temp=0;
      for k=1:6
         temp=temp+mv(i)*mv(k)*(g(i,k)-j*b(i,k))*exp(j*(th(i)-th(k)));
      end
      pcal(i)=real(temp);qcal(i)=imag(temp);
   end

% The mismatches

     delp=p-pcal';
     delq=q-qcal';

% The Jacobian matrix

      for i=1:5
         ii=i+1;
         for k=1:5
            kk=k+1;
            j11(i,k)=mv(ii)*mv(kk)*(g(ii,kk)*sin(th(ii)-th(kk))-b(ii,kk)*cos(th(ii)-th(kk)));
        end
        j11(i,i)=-qcal(ii)-b(ii,ii)*mv(ii)^2;
     end

     for i=1:5
        ii=i+1;
         for k=1:5
            kk=k+1;
            j211(i,k)=-mv(ii)*mv(kk)*(g(ii,kk)*cos(th(ii)-th(kk))-b(ii,kk)*sin(th(ii)-th(kk)));
        end
        j211(i,i)=pcal(ii)-g(ii,ii)*mv(ii)^2;
     end
     j21=j211(1:4,1:5);

     j12=-j211(1:5,1:4);
     for i=1:4
        j12(i,i)=pcal(i+1)+g(i+1,i+1)*mv(i+1)^2;
     end

     j22=j11(1:4,1:4);
     for i=1:4
        j22(i,i)=qcal(i+1)-b(i+1,i+1)*mv(i+1)^2;
     end

     jacob=[j11 j12;j21 j22];  
     delpq= transpose([delp(2:6) delq(3:6)]); 
     corr=solveLS(jacob,delpq);  
     th=th+[0;corr(1:5)];
     mv=mv+[0; 0; mv(3:6).*corr(6:9)]; 
     del=max(abs(delpq));
     index+1;
  end