I did some testing with the different nightly releases. It appears the change occurs between Ionic Package: 1.0.0-beta.4 Antimony Antelope (2014-05-07) and Ionic Package: 1.0.0-beta.5 Barium Bobcat (2014-05-14). Is there a changelog I can take a look at?
The duplicate content only occurs AFTER clicking on a element and changing to a child page. On returning, the background on the ion-content is “frozen” on a duplicate of the initial view. Very odd.
I imagine it has to do with the change to the ui router… ui-router: upgrade to angular-ui-router v0.2.10 (b9353e71, closes #941)