Offboarding Checklists not getting triggered in case of back dated last working days

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Our scenario is as follows:

Offboarding checklist has been created on resignation action, which triggers 20 days prior to resignation action effective date.

The employee submitted their resignation on the 7th of October, last working day is 7th November. However, today (29th October), the manager approves the resignation and changes LWD to 27th October (back dated as per today).

The resignation goes through but the checklist does not get triggered. Can anyone help with why it did not happen? How can we handle this scenario?

 

Here is the setup screenshot

Version

20 C