Reproduction steps:
1. Open the attached project “ReproProject”
2. Build a project using Build → Build Project - Process Test Shader
3. Wait for the process to finish
4. Observe the result in the Console window

Actual result: The build completes with 2 errors, “Trying to access subshader 1, but shader 'Shader' has only 1 subshaders.”
Expected result: The build completes without errors

Reproducible in: 2023.2.0b1, 6000.0.67f1, 6000.3.8f1, 6000.4.0b8, 6000.5.0a6
Could not test with: 2023.1.0a26 (crashes, more information can be found in the internal notes)

Reproducible on: Windows 11
Not reproducible on: No other environments tested