Played around with it for 2-3 hours and I wasn't able to reproduce the issue, Which model are you using, what method did you use to root. Is there a particular amount of time that leads to the Transition Scale reverting or is it possibly when the device is rebooted.
Being unable to reproduce so far I am guessing it's one of three things off the top of my head:
- A system application is triggering a conflict requiring the default value.
- The change is not being saved in a persistent state (reboot clears it)
- A Timeout based on the setting not being applied as the file is in use ? (It's a long shot maybe reboot after change?)
See if you can't narrow down when the setting is returning to default so others can reproduce.