First off I hope you saved the scenario under a slightly new name before you started making changes. Suggest you look at
http://www.wargamech.ca/wc/acwgc/engineering/for an introduction to the editor.
Next if you're using the AI to test the scenario you will need to set the AI values in the editor. See the Help files under Header Dialog paying attention to the section covering AI values and Flags. These determine the action of the AI, whether it attacks, defends, how hard it does either and whether it follows scripts. If you set the value for one side to 2 it will not take any actions unless there are scripts. If you set the value to anything but 2 the AI will ignore scripts. The Flags value determines whether the AI attacks or defends with all units or as the situation develops.
John's comment on Fixed unit release is correct and this could be the cause of the units moving. Another thing to consider is if units are fixed you need to set a release time or they will remain fixed for the entire scenario unless the enemy releases them. You can View, Add releases in the Editor under the Units tab.