running UIAutomation script in many macs?

I could create and replay the following script very well in the mac I Use.

  var target = UIATarget.localTarget();

  UIATarget.localTarget().delay(15);

  target.frontMostApp().mainWindow().tableViews()[0].textFields()[0].tap();

When I run the above script in another mac, It shows error in the 3rd line. after changing the above script's third line as following, it is replaying fine.

  target.frontMostApp().mainWindow().tableViews()[1].textFields()[0].tap();

Just I have changed tableview's index from 0 to 1. How can I achieve this in multiple mac systems? Both mac are having same xcode version(xcode 5) and simulator version(6.1) and mac version.Why Instruments are taking scripts API differently in different macs?