Modifiers On Copied Order

Hello

I have created a simple list modifier for discount. I am able to apply the modifier to an order after going to Actions --> View Adjustments .

However the problem is when I create a new order by 'copying' it from an existing SO. The view adjustment field is greyed out and gives the following note :

"Change in the order level adjustment will not be applied. This is because one of the order line is frozen"

I tried searching for anything related to the message in the metalink but did not get any solutions'

It will be really helpful if anyone could share what could be the issue.