[Affected versions]:

• Firefox Nightly 113.0a1 - Build ID: 20230322211554

[Affected Platforms]:

• Windows 10 x64
• macOS 12.4
• Linux Ubuntu 20.04 x64

[Prerequisites]:

• Have a VPN client connected to a US server (for users located outside the US).
• Have the nimbus.debug pref set to true.

[Steps to reproduce]:

1. Open the browser from the prerequisites.
2. Copy and paste the following link in a new tab:
   about:studies?optin_slug=showing-3rd-sponsored-tile-on-the-newtab-page&optin_branch=treatment&optin_collection=nimbus-preview
3. Open a new tab and make sure you have 3 Sponsored Top Sites.
4. Press the Ctrl+N shortcut to open a New Firefox Window.
5. Observe the Sponsored Top Sites.

[Expected result]:

• All 3 Sponsored Top Sites are displayed.

[Actual result]:

• Only the 2 Sponsored Top Sites via adM are displayed, the Pocket one is not displayed.

[Notes]:

• I was not able to reproduce the issue on Beta 112.0b5.
• The issue is cleared if the tab is refreshed and doesn’t reproduce anymore when opening new Firefox windows.
• Here is a screen recording of the issue.