Created attachment 728239 [details] test case Marionet is interpreting the System element #system-banner I have done some research and cannot see any related Gaia v1-train commits to the System app that might have caused this to change. I have also not changed my marionette version. Looking back over some old HTML the elements have not changed at all.
I trued to find this element and could not find it any more. As this is Gaia v1-train it looks like the bug is not valid any more