Bug When I use blocks "wait 3 seconds"

Hi, i have some problem, can you help me?
I have screen which shows image, i made the image turns every 3 seconds using block (i name it “index”) variable and lists. I connect the image to a new screen which led the user to open a webview to a blog about the image the user already click. I also use block “index” variable and lists to connect the image into the link which the image talking about. The problem is, when i click the image in the screen1 and the open screen2 (webview), and then back again to screen1 rapidly, my image become turns so fast, and sometime random. It does not turns every 3 second like before. Can you help me with that?