https://bugs.freedesktop.org/show_bug.cgi?id=77009
--- Comment #9 from Christian König deathsimple@vodafone.de --- (In reply to comment #7)
Created attachment 96914 [details] dmesg after switching to 25hz and back to 24hz
Those logs doesn't contain a mode switch, are you sure you actually grabed the right log?
Please also try changing the mode directly from the command line with xrandr.