Steps to reproduce:

Actual results: Only white line is visible in the Game view

Expected results: Both red and white lines are visible in the Game view

Reproducible with versions: 6000.6.8f1, 6000.7.0b7, 7000.0.0a11

Not reproducible with versions: 6000.6.7f1

Tested on (OS): macOS 27.0, Ubuntu 24.04

Notes:

Reproducible on a fresh project
An unmasked line that crosses the mask is drawn only inside the mask, i.e. it takes the other line's Mask Interaction.

Also reproduces with:
- TrailRenderer in Play mode: a "None" trail is clipped to inside or outside the mask, matching another trail that uses the same material.
- Material "ParticlesUnlit" instead of "Sprite-Unlit-Default".
- Reopening a saved scene: unmasked lines are already missing when the scene loads.

Does not reproduce when:
- "Line Normal" uses a different material, or a copy of the same material.
- "Line Normal" has any MaterialPropertyBlock assigned through script.
- "Line Masked" Mask Interaction is set to "None".
- The renderers are Particle Systems with mixed Mask Interaction settings.