Large feathered selections suddenly no longer produce correct soft transitions in Curves and Levels. Very large feather values behave like much smaller ones.

A serious problem appeared suddenly yesterday in Photoshop.

My long-used workflow with large feathered selections no longer behaves correctly during direct adjustments such as Curves, Levels and Saturation.

Reproducible issue:

• Large image
• Large selection area
• Feather values between 250 px and 700 px
• Direct adjustment via Curves / Levels

Expected result:
A very broad and soft tonal transition.

Actual result:
The transition remains extremely narrow, visually similar to a much smaller feather radius.

Important observations:

• The same workflow functioned correctly until yesterday
• Feather is actually stored in the selection (verified with Ctrl+J transparency test)
• The problem specifically affects practical adjustment behavior during Curves / Levels operations
• Reproduced after complete clean reinstall
• Adobe Cleaner Tool used
• Preferences reset
• GPU disabled and tested
• Multiple Photoshop versions tested
• Same behavior on a new Windows user profile

This seriously affects fast local correction workflows based on large feathered selections.

Attached screenshots show the problem visually.

Any sugestions?