Save form keeps popping up when changing lines when shipments match approval level is set to 2-way

Hi Experts,

     I just want to ask what part of the trigger do I need to look up. Since in the PO form, when the line shipments were entered and the match approval level is in 2-way, when I close the shipments form and go to the next line. The save form popped out and asking to save the changes. also Even when I'm not changing anything, just as long as I entered the shipments of the line and it was already set to 2-way.. when I go back to the PO form and go to the next line with the