The page messages are displayed on every next page. For example: Invalid Password try -> Message is displayed on the login page -> Go to hompage and the message is displayed again.
I tested the error on multiple devices and even on multiple websites (Official Magento Demo, Venroy, Solgirl, ...). On my installation and even on the official magento demo shop the message is displayed on every page again and again.
Looks like a bug, report it in the issue tracker: https://github.com/magento/magento2/issues
Have you got any solution for this issue? Please let me know if you have found any clue to solve this problem.
I got the same issue on magento 2 version 2.0.7 . Let me know if you got any idea related on this issue.