ID 468608 - Custom user knobs created in at root level duplicate when script is closed and re-opened

Problem summary
Opening and Closing a script with a custom user knob/tab on the root node duplicates the custom knob/tab.

Customer reported version
nuke.12.2v5

Customer reported platform
windows10

Steps to reproduce

1) Open a new Nuke session.

2) Within the Node Graph, press 's' to access the Project Settings (root level)

3) With the Project Settings window open, right-click and select 'Manage User Knobs..'

4) Once the dialogue box opens, Add a new custom knob (of any variety). This will create a new tab called 'User' containing your custom knob.

5) Close or clear the script (keeping the Nuke session open)

6) Re-open the closed/cleared script and view the Project Settings

Expected behavior
Closing and opening a script when a user knob is added to root level should not duplicate the tab or knobs

Actual behavior
When a script is closed or cleared, the custom user knobs should remain without alteration.

Workaround
There is no available workaround at this time.

Reproduced by support
Nuke Studio 13.0v1 - Windows 10, CentOS 7
Nuke 12.2v5 - Windows 10 - MacOS 10.15.6 - CentOS 7 - regression

Unable to reproduce bug in:
Nuke 12.2v4 - Windows 10 - MacOS 10.15.6 - CentOS 7

Earliest version tested
Nuke 12.2v4 - This issue doesn't appear in this version and has regressed