Workflow rule does not trigger/run when the 'field update' field is updated by a finction.

Workflow rule does not trigger/run when the 'field update' field is updated by a finction.

Hi there,

I have found that workflow rules do not trigger when the field that is set as "Field update" is up dated by a function.

I have a DEAL workflow rule set like this,
When do you want to execute this? : *On record action, *field update.
I have created a schedule action.
I have specified a field (on the deal), which is updated by a function.
The function that updates the field is run in a blueprint in the TASK module.

The workflow rule works as expected when the field is updated either manually or by a blueprint on the deal page.
however the workflow rule does NOT trigger when the field is updated by the function (run from a blueprint on a related task), the field updates correctly but the workflow rule does not trigger.

Is this normal?
Is there another way of doing this?
Or is there a work around?

The purpose of this is to have a scheduled workflow rule started on the related deal when the task is 'Marked Complete'. The scheduled action updates a specific field 8 days later.

I have also found that if you use a field update in a task blueprint that updates a field in a deal, any related workflow rules do not trigger.

Thanks in advance!