Changes editing the mission-file inside miz have no effect(?)

I wanna edit the file "mission" from within a miz file, but it does not take the changes.

My procedure:

- copying the "mission"-file from the zip to a normal directory

- renaming it into mission.lua

- opening it in notepad++

- doing my changes (search and exchange one false flag into true which should change the radio transmit freq. for my LSO-calls from FM to AM

- saving the file

- deleting the old from the zip

- copying the new into the zip

- opening it in the mission editor - no change

- rechecking it in the miz - changes still there - resaving the mission as new miz -> rechecking the mission file -> changes gone

What do I wrong?

I make such changes to the mission file without issue. My procedure:

Open .miz in WinRar

Open mission file in Notepad++

Make file changes and save in Notepad++

Close file in Notepad++

Now I get a message in WinRar like "do you want to save changed file?"

Answer yes and close WinRAR

.miz now has my changes

I think perhaps the file compression program you are using does not give you the option of saving the changed .miz file.

The thing is:

The change IS in the mission file, but still it says FM in the radio-message-trigger instead of AM.

Edit:

And when I save the (changed) mission from within the ME again, the change is gone in the mission file.