New shipment includes some lines of an old closed shipment


I have a problem in a brand new shipment has picked up three lines of an old closed shipment.

I cannot remove that unwonted picked lines. If i try to remove there is an error saying

" The lines cant removed whilst work exists. "

I need to know why those lines are selected ?

Where can be the problem in shipment or any other ?

Please give a solution to fix this issue.