I tried this new feature when it was out. It is a great add to collections but now I see I cannot change the thumbnail for my embedded web page. When I publish the collection the thumbnail reverts to its original image (if any).
In Decembers's release notes I see this listed:
Could this have anything to do with the behavior of the embed's thumbnail?
@AGP -- This is a bug and is not expected (it's unrelated to the item in the release notes you mentioned). We can reproduce this issue and are looking into the cause.
Once we isolate the problem, we'll plan to deploy a fix in an upcoming update. I'll post more information here when it is available.