Is this happen on a particular app or on all of them?

What version and build of InteractBuilder are you using and also does this situation occurs on every app? Thank you for your feedback.

Yes Cathy, you can do  this by using an empty Text element with SetText behavior on the text element as in the attached example:
251 - SetText.zip

Yes Cathy, you can do  this by using SetText behavior as in the attached example:
251 - SetText.zip

Try to delete InteractPlayer from your iPad then reinstall it. Thank you for your feedback.

You can duplicate the element then in the element properties to assign the same image as the original sky

Well you can use the same sky element so it wont add to your app size.

Yes you set it right but since is a Random location you can't predict the exact place where the star will be placed. But if you want to distribute them evenly there is a solution: Have two copies of the sky. For the first copy have the Constraints : 0,786,512,0; and two extra behaviors: Tap-Hide self and Tap-Show the other sky copy. 
For the other copy have the Constraints of the move behavior: 512,786,1024,0 and also the extra two behaviors as the first  copy. The reason for those two copies is to have the stars place one on the left side of the screen and the other one placed on the right side of the screen. And the reason for the extra two behaviors is to alternate the star location.

That's the only solution I can come up with so far: having multiple transparent elements covering the screen where you want the stars to appear. Then when user taps the transparent element a star will show. I will keep thinking of another solution and I will let you know. Thank you for the feedback.

With a simple behavior no. I suggest having multiple transparent elements covering multiple stars. When the user tap that transparent element the start will show.