Customer's PO column is disable in sales invoice

After update to ERPnext: v12.14.0 n Frappe v12.12.0 yesterday (29 Nov 2020), customer’s Purchase Order is disable with pink background color ie can not edit customer PO . I am using Ubuntu 18.04TLS and bypassing Sales order, deliver note and pick list etc in the workflow of Sales procedure and go directly from customer purchase order to sales invoice. it means that I’ll key in customer PO number directly when invoicing. Now I have problem, my invoice printing do not show customer’s PO number. Thks

Have you made any customizations like writing a script?

This is working fine for me:

Thks for prompt reply.
No I do not write any script. It has been normal before updating ERPnext and Frappe using Bench update command.
unlike previous version, I can key in PO number but it is not saved, it is blank on next opening of the invoice.
po_no in table “tabSales Invoice” in the database is found to be blank.

BUG link: BUG: V12 Sales Invoice is Removing Customer PO Number

BUG fixed in Frappe V12.13.0 n ERPnext V12.15.0