ID 608767 - Removing entries from Pulldown/Enumeration knobs can cause errors and prevent Nuke scripts from loading correctly

Problem summary:
Removing entries from Pulldown/Enumeration knobs can cause errors and prevent Nuke scripts from loading correctly
 
For Group nodes specifically, this causes them to eject their contents into the main Node Graph.
 
Customer reported version:
Nuke 16.0v4
 
Customer reported platform:
Alma 9
 
Steps to reproduce:
1) Launch Nuke and create a Group node in the Node Graph
2) In the Group's Properties, right-click and select Manage User Knobs...
3) Press the Add button, and select Pulldown Choice
4) Give the knob a name and at least two Menu Items, such as "a" and "b"
5) Press OK and Done to add the knob to the Group
6) Select the second Menu Item in the Group's Properties, "b" in this example
7) Right-click and use the Manage User Knobs... > Edit action to remove both Menu Items from the knob, then save your changes
8) Copy/Paste the Group into the Node Graph. Alternatively, save and reopen the .nk script
9) Observe the Bad value for <knobname> : 1 error, and note how the Group's contents are now in the main Node Graph: 
 
Expected behavior:
Pulldown knobs that have their options adjusted or reset should not prevent Nuke from loading the Node Graph correctly.
 
Actual behavior:
When a node has a Pulldown/Enumeration knob and a Menu Item with a non-zero index is selected, removing Menu Items will put the node into an errored state. This occurs if the Menu Item(s) are removed via Python, Manage User Knobs, or the Knob Editing interface (Ctrl+Alt+E).
 
If only the selected Menu Item is removed and that item had the highest index, the error will instead read "missing value". For example, if the knob had "a", "b", and "c" as Menu Items and "c" was selected, removing only this entry while leaving "a" and "b" untouched would produce the "missing value" error message.
 
In previous versions of Nuke, the error message in both scenarios would be "input already correct", but the behavior is the same. 
 
Workaround:
No known workaround at this time.
 
Reproduced by Support in:
Nuke 16.0v6 - Windows 11, macOS 14 Sonoma
Nuke 16.0v1 - Windows 11
Nuke 15.0v1 - Windows 11
Nuke 14.0v1 - Windows 11
Nuke 13.0v1 - Windows 11
 
Earliest version tested:
Nuke 13.0v1 - This issue appears to be in all tested versions of the product