I have a particular situation where I can't close a Issue that has some subtasks.

In the Issue Workflow, I have "New" -> "In Progress" -> "Closed", and you can't go from New -> Closed without passing through "In Progress".

I have a "Field permission" configuration where the field "Due date" is Required, then the status is "In Progress".

I implemented this configuration when having some issues already in the state "In Progress" with a parent task.

A parent task's "Due Date" is the last date of its subtasks.

My situation is I have a Parent issue in "New" state , with all subtasks closed and without a "Due Date". When I try to put my parent task "In Progress" so I can then, "Close" it. I'm not allowed 'cause I need to put a "Due date" in it, and I can't fill a due date in a Parent task.

The Redmine version I'm using in production is 2.6.0-stable.

Let me know if you need more information.