Resetting vibrance and saturation causes loss in auto tune adjustments

ACR version: 15.5.1.1597

Bridge version: 12.0.4.286

Repro steps:

1. Select a large amount (more than 50) of photos in Bridge and open in ACR.

2. Select all photos by Ctrl+a and click "auto" to apply auto tune adjustments.

3. Double click on vibrance and saturation sliders to reset their values to 0. At this point all photos still have the auto tune adjustments when viewing them in ACR.

4. Click "Done" to save and exit ACR.

5. When reopening the photos in ACR, many of them lost the auto tune adjustments.