intermediate variables influnences in a for loop of MATLAB code

Hi everyone,

I have a problem about intermediate varaibles in a for loop. It's part of MLP code, for simplicity I don't write it down here. In the last section of the for loop, it is

 W1Ex=W1Ex+lr*dW1Ex;
 W2Ex=W2Ex+lr*dW2Ex;
 W2=W2Ex(:,1:HiddenUnitNum);     

 end

And now I want to add intermediate varaibles as

 W1_2Ex=W1Ex+lr*dW1Ex;
 W2_2Ex=W2Ex+lr*dW2Ex;
 W2=W2_2Ex(:,1:HiddenUnitNum);
 W1Ex=W1_2Ex;
 W2Ex=W2_2Ex;

 end

And Since W1_2Ex and W2_2Ex only exist in this part, the rest of the loop remain the same. I don't know why the simulation under these two scenarios are different. Actually, the changed one did not converge. Moreover, when I switch back to the orignal code（without intermediate varaibles）. The results are wrong too and I have to restart MATLAB to run it again to get the right answer! Could someone give me some hints!