If a stack update fails, a subsequent stack-show will show the old parameter values rather than the ones we attempted to update with. It may even error out due to missing user parameters. There is already a fix (under https://bugs.launchpad.net/heat/+bug/1477812) upstream in Liberty, and which has been proposed for backporting to Kilo.
both required, required+default values and unused parameters are being updated to show the most recent update attempt.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2015:1865