ticket : initial due date

Hello, 
When I copying a ticket, the initial due date is copied but it is impossible to modify it even with administrator access.
normal ? how to do ?

Thanks for your feedback
Regards,

You mean Ticket or Simple Ticket ?

Hi,
Ticket

Regards,

Doc:
Initial due date of the ticket set as read only if it is calculated from the setting of “delays for tickets”

 

Hi, 
Unfortunately I don't have anything in the section “delays for tickets”.
I pushed my tests with more details, and I qualify my information.
If I duplicate a ticket where the date is "read only" the copy is "read only" if I copy a ticket where the date is editable the copy is editable.

However I don't understand, why I have some tickets that are read only. strange

Thanks for your support
If I have more information I will come back on the subject

Regards,