Update baq to close PO release

I created an updateable BAQ to update PO release due date - works fine. I added the field PORel_OpenRelease to be updated (so I can close all the PO releases left open) - I get list - (it does list all the open PO releases) - I double click and uncheck the OPEN REL check box - when I hit UPDATE I get the following error

Severity: Exception, Table: PORel, Field: , RowID: 81735df9-c6d4-422c-93df-9a6e4bdd1269, Text: Release is closed
Query returned 1 row(s).

However, if I then double click the line again - and select the box (to put tick mark back on) - then update - it processes.

What am I missing?

Are you checking the status of the change between saving?