P: PS 27.5 & Beta Can not Save Adjustment Preset for the Green Channel in Curves Adjustment Layer

System Info:

-OS: macOS Tahoe 26.1 
-Hardware: Apple M2 Max (Apple Silicon) 
-Photoshop Version: 27.5 / 27.6 beta

Description:
The new Adjustments Panel (UXP-based) fails to save or preview custom presets if the Green channel of a Curves layer has been modified. This happens even with a neutral point (Input 128 / Output 128).

Steps to Reproduce:

-Create a new RGB document (8 or 16 bits).
-Add a Curves Adjustment Layer.
-Modify only the Green Channel (even a neutral point like 128/128).
-Try to save as a new Preset using the (+) icon in the Adjustments Panel.

Actual Result:
The thumbnail appears with a red diagonal line and the preset is not functional. The folder ~/Library/Application Support/Adobe/Adobe Photoshop [Version]/Presets/Adjustment Presets remains empty (no .psap file created).

Expected Result:
The preset should be saved correctly, as it does with Red and Blue channels.

Additional Discoveries (Key for Devs):

-The bug occurs only in the Curves adjustment layer. 
-The bug does not occur in Lab Color mode (modifying the 'a' channel works fine). 
-The bug does not occur when saving via the old Properties menu (Save Curves Preset... as .acv).

It seems to be a serialization error specifically linked to the Green channel index in the new UXP Adjustments Panel.