Neural Filters: Skin Smoothing disappears when opening Smart Filter Blending Options

Summary
On an affected two-person portrait, Neural Filters > Skin Smoothing works initially when output as a Smart Filter. Simply opening that filter's Blending Options makes the smoothing disappear, even when opacity stays at 100% and no setting is changed. Clicking OK leaves the effect missing. Other documents do not show the problem.

Environment
Photoshop desktop 27.11.0; Camera Raw 18.7.
Windows 11 Pro, version 10.0.26300 (build 26300).
Affected test document: 9504 x 6336 pixels, RGB 16-bit, ProPhoto RGB, layered TIFF. A fresh test copy was created from Lightroom Classic using Open as Smart Object and initially contained only one embedded RAW Smart Object, with no other Smart Filters.

Steps to reproduce with the affected image
1. Open the two-person portrait as a Smart Object.
2. Open Filter > Neural Filters > Skin Smoothing.
3. Apply smoothing to both detected faces. In the test, Blur was 96 and Smoothness was 0 for each face.
4. Set Output to Smart filter and click OK. The smoothing is visible at this point.
5. Right-click the Neural Filters entry in the Layers panel and choose Edit Smart Filter Blending Options.
6. Leave blending mode at Normal and opacity at 100%, then click OK.

Expected result
Opening and confirming the dialog without changes should preserve the existing appearance. Lowering opacity should reduce the effect normally.

Actual result
The smoothing disappears on opening the dialog and remains missing after confirmation, although the Smart Filter entry is still present. Changing opacity from 0% back to 100% does not restore it in the failing configuration.

Comparative tests
- On the same affected photo, a Skin Smoothing Smart Filter containing only the default first face could be blended normally.
- Selecting the second face when creating another filter was not sufficient to isolate it: inspection of the saved NF_UI_DATA / spl::cropStates showed both a default first-face entry and a second-face entry. That configuration still failed.
- A separate single-face document and a simple single-face test image supported normal opacity changes.
- Testing an 8-bit version and saving the affected content as PSB did not resolve the issue. The failure also occurred in the fresh RAW Smart Object test copy, so it was not limited to the original document's more complex retouching stack.

Non-rasterizing workaround verified
Two instances share one embedded source Smart Object. Inside that source, two visibility-only Layer Comps provide (a) the full photo and (b) a masked RAW instance showing only the second person's head area, with the rest transparent. The parent instances select different comps and each has its own Skin Smoothing Smart Filter. The second person's filter then detects only one face; the full-photo instance processes the default first face.

With this setup, the filters' Blending Options worked, including 0%, 50% and 100% checks for the previously failing second-person case. Editing the shared RAW exposure, saving the source, and then restoring the exposure updated both parent instances; both filters remained adjustable after recalculation.

This suggests a connection with multi-face Skin Smoothing Smart Filter recalculation, but the root cause is not confirmed. Please investigate why opening Blending Options invalidates the effect in the failing configuration. I need to preserve editable Smart Objects and automatic updates when the source is edited.