“AssertionException: Assertion failure. Value was False” errors are thrown when dragging UXML Asset into the UI Builder Hierarchy after editing a Template Instance

Reproduction steps:
1. Create a new project
2. Create two UI Document Assets (Create > UI Toolkit > UI Document)
3. Open one of the UI Document Assets in UI Builder and drag other Asset from Project tab into the Hierarchy panel
4. Right-click on the newly added UXML Instance and select "Create Template" option
5. Drag the newly created UXML Template into the Hierarchy panel
6. Right-click first added UXML Instance, select “Open Instance in Context” option and save changes when prompted
7. Drag any available UXML instance, save changes and navigate back to the parent UXML file
8. Right-click newest added UXML Instance and select “Open Instance in Context” option
9. Drag any available UXML Instance and observe the Console

Actual result: Multiple "AssertionException: Assertion failure. Value was False. Expected: True" errors are thrown
Expected result: No errors or warnings are thrown

Reproducible with: 6000.4.11f1, 6000.5.0b12, 6000.6.0a7
Not reproducible with: 6000.3.17f1, 6000.4.10f1
Couldn’t reproduce with: 6000.0.76f1 (No option to create Template)

Reproduced on: Ubuntu 24.04, macOS Tahoe 26.5 (M4)

Note: Sometimes UXML Instance preview remains visible until window is reopened