A few things to verify. Start the Harmony client and check the Sunset time at the bottom of the screen for the expected value. Check the Days of the Week for the Action to be sure a day was not missed. Have the telnet trace cover the Action that worked through a failure. If this is another variant of the problem with Actions not being reenabled the Action that performed the Effects as expected is actually where the failure occurred. Need a telnet trace that covers the day before where the Action triggered to be sure it completed all the required steps. If a reenable is missed, it will not trigger the next day.
Post the Action, it might have something special that I can attempt to recreate.