I choose SetupRegionModel, and then click 'Back' in the browser, not submit, and 2 other fragments are shown:
After further investigation, we concluded that the Simulation page is cached by the browser. So, when we click the 'Back' button in the browser, we get the latest cahced version of the page. After a refresh, the fragments are reloaded correctly.
We should investigate whether we could force the browser to not cache that page, but always reload it.
Otherwise, we could mitigate this problem, by adding a 'Cancel' button in our application, SetupRegionModel page, near 'Submit', so users would be inclined to use that one instead of the 'Back' button in the browser.