Workflow is not triggered with Supervise rule and field update

Workflow is not triggered with Supervise rule and field update

Hi!

I have created a Supervise Rule, which triggers after 5 days a mail to the customer.
To avoid sending multiple mails to the customer I have created a checkbox ReminderSent in the ticket properties, which is set to true by a field update.

Now I want to add a Comment to the ticket by a custom function by executing a Workflow Rule.
The configuration works, when I check the checkbox ReminderSent manually, but when the checkbox is updated by the Field update, the Workflow for creating the comment is not working.

Workflow settings:


Ticket properties:


Supervise Rule:


Is there a setting, that I missed to execute the Workflow rule or is this a bug?

Thank you in advance and kind regards