Hello new_tesla;

To add to Hati's post, here is information you might want to look at concerning MicroWin.

This is taken from the S7-200 System manual, which I suggest you consult as long as you are working with these CPUs.

https://support.industry.siemens.com/cs/us/en/view/1109582

You will find the link to the Cross Reference Table in the Debug menu of MicroWin.

Hope this helps,

Daniel Chartier

Henry1675

If you don't provide the whole picture its hard to tell whats going on.
Show the complete network 2 if you can. (The one with M3.1 = on)

I bet m3.1 is being reset in network 2 and later on (your second picture) M3.1 is set again. (set/reset loop)
This is what I think whats happening. That's why  you see in network 3 m3.1 = off.

 The real issue is overlapping memory areas. MD3 is used elsewhere in the program, and it's overlapping with M3.1.