Steps to reproduce:

Open the attached project
In the Project window, go to Assets/PB/UXML and select HintedPair.uxml
If the Editor does not crash, double-click to open it in UI Builder window
Observe the Labels in the UI Builder window

Actual results: The issue is inconsistent and can lead to multiple outcomes:

Editor crashes on UXML selection or when attempting to open the UXML in the UI Builder window
A "Header should not already be rooted when this is called" error message is thrown after selecting the UXML. UXML opens, labels are rendered
No error is thrown when UXML is selected; the UXML opens, but the Label's text is not rendered

Expected results: Editor does not crash on UXML selection or when opening it in the UI Builder window. The text is rendered and is not malformed. No errors are thrown when attempting to open the UXML asset

Reproducible with versions: 6000.7.0b6, 6000.7.0b7, 7000.0.0a8, 7000.0.0a12

Not reproducible with versions: 6000.0.85f1, 6000.3.26f1, 6000.6.7f1, 6000.7.0b5, 7000.0.0a1, 7000.0.0a7

Tested on (OS): macOS 27.0.1 (Apple Silicon)

Notes:

Full error message:
- Header should not already be rooted when this is called
  UnityEngine.UIElements.ATGTextJobSystem/GenerateTextJobData:Execute (int)
  Unity.Jobs.IJobForExtensions/ForJobStruct`1<UnityEngine.UIElements.ATGTextJobSystem/GenerateTextJobData>:Execute (UnityEngine.UIElements.ATGTextJobSystem/GenerateTextJobData&,intptr,intptr,Unity.Jobs.LowLevel.Unsafe.JobRanges&,int) (at /Users/bokken/build/output/unity/unity/Modules/ManagedKernel/Managed/Jobs/IJobFor.cs:86)
First lines of the crash stack:
- Obtained 74 stack frames
  #0 _platform_memset
  #1 tt_glyph_load
  #2 UNITY_FT_Load_Glyph
  #3 FT_Get_Advance
  #4 hb_ft_get_glyph_h_advances(hb_font_t*, void*, unsigned int, unsigned int const*, unsigned int, int*, unsigned int, void*)
  #5 _hb_ot_shape
  #6 hb_shape_plan_execute
  #7 hb_shape_full
  #8 TextShapingService::ShapeText(unsigned short const*, int, bool, hb_font_t*, bool, hb_script_t)
  #9 FontAsset::GetMissingGlyph(int)
  #10 TextShapingService::ShapeSegment(TextSegment&, core::vector<Text::Glyph, core::allocator<Text::Glyph, 0ul>>&, icu_73::UnicodeString&, int, int, TextGenerationInfo const&, core::vector<bool, core::allocator<bool, 0ul>> const&)