Hello.
Hopefully there is just something I am missing here but I have found that when following the platform tutorial (the jungle one) and implementing the enemy AI the enemy goes back and forth between the edge markers for the first few second but eventually goes beyond them.
You can watch this for a few moments to see what I am saying:
http://gassymule.site50.net/UHS/
Here is the actual cap file:
http://gassymule.site50.net/UHS.capx
As you will see from the capx the logic is pretty simple.