title: DFP issue : div element is already associated with another slot
body: <p>I am new to DFP. I am trying to show an image from collection of images to a single slot with time interval of 5 sec. What i found is some images get display in 5sec and some came and changes within 2 or 3 sec. This inconsistency looks very ugly. I tried to debug with google force console and found this logs :</p>
  
  <pre><code>Status  Time    Description
  Information Start   Created slot: /116095010/marcom_0
  Information 1 ms    Google service JS loaded
  Information 1 ms    Created service: publisher_ads
  Information 2 ms    Associated service "publisher_ads" with slot "/116095010/marcom".
  Information 2 ms    Invoked queued function. Total: 1. Errors: 0.
  Information 2 ms    Setting targeting attribute user_state with value visitor for service publisher_ads
  Information 2 ms    Setting targeting attribute utm_source with value dfp for service publisher_ads
  Information 2 ms    Setting targeting attribute utm_campaign with value Nag_StartMyFreeTrial_Desktop_min for service publisher_ads
  Information 2 ms    Setting targeting attribute utm_medium with value internalcpc for service publisher_ads
  Information 2 ms    Setting targeting attribute undefined with value 20500102 for service publisher_ads
  Information 2 ms    Using asynchronous rendering mode to fetch ads.
  Warning 3 ms    **The ads cannot be refreshed because the GPT implementation Javascript is not yet loaded.**
  Information 4 ms    GPT implementation fetched.
  Information 8 ms    Calling fillslot.
  Information 34 ms   Fetching ad for slot: /116095010/marcom
  Information 46 ms   Invoked queued function. Total: 1. Errors: 0.
  Information 432 ms  Receiving ad for slot: /116095010/marcom
  Information 433 ms  Rendering ad for slot: /116095010/marcom
  Information 433 ms  Completed rendering ad for slot: /116095010/marcom
  Information 824 ms  Created slot: /116095010/collection-carousel-top-desktop_0
  Information 824 ms  Associated service "publisher_ads" with slot "/116095010/collection-carousel-top-desktop".
  Information 824 ms  Invoked queued function. Total: 2. Errors: 0.
  Information 824 ms  Setting targeting attribute user_state with value visitor for service publisher_ads
  Information 824 ms  Setting targeting attribute utm_source with value dfp for service publisher_ads
  Information 824 ms  Setting targeting attribute utm_campaign with value Nag_StartMyFreeTrial_Desktop_min for service publisher_ads
  Information 824 ms  Setting targeting attribute utm_medium with value internalcpc for service publisher_ads
  Information 824 ms  Setting targeting attribute undefined with value 20500102 for service publisher_ads
  Information 824 ms  Using asynchronous rendering mode to fetch ads.
  Information 824 ms  Refreshing ads.
  Information 870 ms  Fetching ad for slot: /116095010/marcom
  Information 871 ms  Service is already enabled
  Information 871 ms  Calling fillslot.
  Information 881 ms  Invoked queued function. Total: 2. Errors: 0.
  Information 905 ms  Created slot: /116095010/collection-carousel-top-desktop_1
  **Error 905 ms  Div element div-gpt-ad-1440572949275-0 is already associated with another slot.
  Error   905 ms  Exception when invoking function: Cannot read property 'addService' of null**
  Information 905 ms  Invoked queued function. Total: 2. Errors: 1.
  Information 905 ms  Setting targeting attribute user_state with value visitor for service publisher_ads
  Information 905 ms  Setting targeting attribute utm_source with value dfp for service publisher_ads
  Information 905 ms  Setting targeting attribute utm_campaign with value Nag_StartMyFreeTrial_Desktop_min for service publisher_ads
  Information 905 ms  Setting targeting attribute utm_medium with value internalcpc for service publisher_ads
  Information 905 ms  Setting targeting attribute undefined with value 20500102 for service publisher_ads
  Information 905 ms  Using asynchronous rendering mode to fetch ads.
  Information 905 ms  Refreshing ads.
  Information 953 ms  Service is already enabled
  Information 953 ms  Calling fillslot.
  Information 955 ms  Invoked queued function. Total: 2. Errors: 1.
  Information 961 ms  Created slot: /116095010/NAG-Visitor-desktop_0
  Information 961 ms  Associated service "publisher_ads" with slot "/116095010/NAG-Visitor-desktop".
  Information 961 ms  Invoked queued function. Total: 3. Errors: 1.
  Information 961 ms  Setting targeting attribute user_state with value visitor for service publisher_ads
  Information 961 ms  Setting targeting attribute utm_source with value dfp for service publisher_ads
  Information 961 ms  Setting targeting attribute utm_campaign with value Nag_StartMyFreeTrial_Desktop_min for service publisher_ads
  Information 961 ms  Setting targeting attribute utm_medium with value internalcpc for service publisher_ads
  Information 961 ms  Setting targeting attribute undefined with value 20500102 for service publisher_ads
  Information 961 ms  Using asynchronous rendering mode to fetch ads.
  Information 961 ms  Refreshing ads.
  Information 962 ms  Service is already enabled
  Information 962 ms  Calling fillslot.
  Information 973 ms  Invoked queued function. Total: 3. Errors: 1.
  Information 1273 ms Receiving ad for slot: /116095010/marcom
  Information 1273 ms Rendering ad for slot: /116095010/marcom
  Information 1273 ms Completed rendering ad for slot: /116095010/marcom
  Information 1277 ms Fetching ad for slot: /116095010/collection-carousel-top-desktop
  Information 1730 ms Receiving ad for slot: /116095010/collection-carousel-top-desktop
  Information 1730 ms Rendering ad for slot: /116095010/collection-carousel-top-desktop
  Information 1730 ms Completed rendering ad for slot: /116095010/collection-carousel-top-desktop
  Information 1733 ms Fetching ad for slot: /116095010/marcom
  Information 2095 ms Receiving ad for slot: /116095010/marcom
  Information 2095 ms Rendering ad for slot: /116095010/marcom
  Information 2095 ms Completed rendering ad for slot: /116095010/marcom
  Information 2099 ms Fetching ad for slot: /116095010/collection-carousel-top-desktop
  Information 2488 ms Receiving ad for slot: /116095010/collection-carousel-top-desktop
  Information 2488 ms Rendering ad for slot: /116095010/collection-carousel-top-desktop
  Information 2488 ms Completed rendering ad for slot: /116095010/collection-carousel-top-desktop
  </code></pre>
  
  <p>This contain 1 warning and two error. I googled it but not get any help.
  I tried to move the refresh code at last of page but that also not help. 
  Please advise.</p>