program behavior due to editor issues

In the attached code adding the two line commands near the top changes the behavior of the program from how it behaved without the line commands. Then I comment out the line commands and the program behavior does not revert to the program without the line commands. I delete the line commands and the program does not revert to the original.

Very confusing.

I have noticed other strange behavior. My code wasn't working as expected. I removed a section of code that looked correct, just to try something. I reinserted the very same section and the program worked as expected. I performed these operations with control x and control v.

I hope I am doing something wrong.

%Molecule trajectory

clf

 xx=1:10;z=[1 0 0 0 0 0 0 0 1 0];stem(xx,z)
 axis ([0 10 0 2]);
 %line([1,4],[1,1])
 %line([6,9],[1,1])

 hold on

 x = 0; y = 0;

 plot(9.5,1.2, 'o')

 dx = .1; dy = .008; N = 200;

 xo = 8.5; yo = 1.5;

    for i = 1:N
     x(i) = xo - i*dx;
     y(i) = yo - i*dy;
     plot(x(i),y(i))
      if x(i)<=1
          plot(x(i),y(i),'o')
          %set(p,'Color','red','LineWidth',1)
          %line([xo,yo],[x(i),y(i)])
          %return
          break
      end

    end

    x1 = x(i)
    y1 = y(i)
    i = 0;

    for i = 1:N
     x(i) = x1 + i*dx;
     y(i) = y1 - i*dy;
     plot(x(i),y(i))
      if y(i)<=0
          plot(x(i),y(i),'o')
          %set(p,'Color','red','LineWidth',1)
          %line([xo,yo],[x(i),y(i)])
          %return
          break
      end

    end

     x1 = x(i)
    y1 = y(i)
    i = 0;

    for i = 1:N
     x(i) = x1 + i*dx;
     y(i) = y1 + i*dy;
     plot(x(i),y(i))
      if x(i)>=9
          plot(x(i),y(i),'o')
          %set(p,'Color','red','LineWidth',1)
          %line([xo,yo],[x(i),y(i)])
          %return
          break
      end

    end

     x1 = x(i)
    y1 = y(i)
    i = 0;

    for i = 1:N
     x(i) = x1 - i*dx;
     y(i) = y1 + i*dy;
     plot(x(i),y(i))
      if x(i) <= 1
          plot(x(i),y(i),'o')
          %set(p,'Color','red','LineWidth',1)
          %line([xo,yo],[x(i),y(i)])
          %return
          break
      end

    end

    x1 = x(i)
    y1 = y(i)
    i = 0;

    for i = 1:N
     x(i) = x1 + i*dx;
     y(i) = y1 + i*dy;
     plot(x(i),y(i))
      if x(i) >= 9.5
          plot(x(i),y(i),'o')
          %set(p,'Color','red','LineWidth',1)
          %line([xo,yo],[x(i),y(i)])
          %return
          break
      end

    end

[cr]

Unable to reproduce your issue. For me, "lines" just create two additional horizontal lines and dont change anything else either in the plot or x1,y1 in command window. Is this a script or a function? If a function make sure your function name and filename are the same to avoid confusing outputs. Create a fresh directory and use scripts if functions dont have any i/o.