Nuxeo Platform navigation is based solely on the JSF library.
Although the JSF library is not designed to take advantage of the Back and Next buttons of the browser, these buttons work in most cases when called on GET actions, but some inconsistent display could happen if used after a user action modifying data. However, those cache-related display inconsistency aren't harmful in anyway for the system.
Those unwanted displays are hard to fix: it could be done by pushing "by hand" some history info into a queue whenever the Nuxeo Platform does a navigation, and try to return to that when an application-based back button is pressed. But this would be quite complex and browser dependent.
So if you're massively using POST action, the solution is to train the users to never activate/use the Back and the Next buttons when using the Nuxeo Platform.