Workflow Scheduler does not move states

Dear all,

I have encountered the following problem:

Presets:

• One Workflow, attached to Post "Workflow 1"
• One Workflow setup: role can move Workflow from "Custom State 2" to "Custom State: Notification"
• Permissions: Participate in workflow, Show workflow state change on node view, Schedule workflow transitions,Administer workflow
• State is set from "Custom State 1" to "Custom State 2" immediately - this works.
• Transition from "Custom State 2" to "Custom State: Notification" is scheduled for midnight next day.
• Attached to the the Transition is a rule to send an email once the state changes.

Expected result:

• On cron run and time being passed: Change the state and execute the rule

Actual result:

• Once cron runs the scheduled change disappears:
  • The node remains unchanged
  • There is no recorded that the state was ever changed
  • the rule does not execute

Thank you for any help or pointers.

Best.