Cursor not moving to next navigation item

In one of our forms there are two text items on users enter some values. The second text item was added in recent change.  In the first text item, next navigation item is filled with the second text item. So ideally when user enters some value in first item and press enter key the cursor should move to second text item. Instead the cursor moves to submit button which causes pop up of unnecessary message due to validation failure. There is no WHEN-VALIDATE-ITEM trigger defined on the first text item. What can be the reason for this and how to