Serial Number Column Missing in PO

[atharva21k]

I am facing this issue while changing the delivery date for a line item in the PO.

So i have a PO with 2 line items and both line items have the same serial numbers assigned to them.

When i am changing the delivery date of 2 line item the serial number column for line item 1 dissappears

Screenshot of line item 2

Screenshot of line item 1

Screenshot of Document flow

We have recently upgraded SAP from 1709 to 2021; the reason to mention this is because this issue is not happeneing in previous system.