After modifying a bar code's object based screening settings, the bar code is no longer live. So you can no longer modify it.
You can no longer change the bar code settings, for e.g., the bar code number, after modifying the screening settings for the bar code. If you try to modify the bar code settings and click Modify in the bar code window, it creates a new bar code instead of updating the selected, existing bar code.
Install hotfix 1204012 build ArtPro 12.1.1 build 144 or install versions 12.1.2 or newer.
The same problem happens when you modify screening on a bar code in the Apply ArtPro Action List task in Automation Engine 12.1.1. See this hotfix article for more information: