White outline appears around masked or scaled layers in fullscreen preview (Mac Studio / Metal)

Issue:

When using fullscreen playback (via Mercury Transmit) on a secondary monitor, Premiere Pro shows a white outline around any scaled-down or masked video/graphic layer. This white outline also appears on the Program Monitor during real-time playback. The white edges do not appear in the final export.

System:

• Mac Studio M2 Ultra with dual Apple Studio Displays + mirrored client monitor (4K Samsung OLED TV)

• macOS Sonoma (latest OS, issue present across all OS updates in the last year+)

• Premiere Pro (latest version, issue present across all versions in the last year+)

• Renderer: Metal (cannot be changed)

Steps to Reproduce:

1. Create a sequence (any resolution)

2. Add a video or graphic

3. Scale it or apply a mask (with or without feathering)

4. Enable fullscreen playback on an external monitor

5. Observe white edges appearing in real-time playback on the external monitor and on the Program Monitor

6. Note the white edges do not appear in the final exported video

Additional Details:

• Rendering the timeline removes the issue but breaks real-time editing performance

• “Composite in Linear Color” ON or OFF makes no difference

• Disconnecting the mirrored 4K OLED TV or changing which monitor has fullscreen playback does not affect the issue

• I also have an M1 Macbook pro (same OS and Premiere version) which does not have this issue

I attached 2 screenshots. It's a graphic, which has crop, it's scaled down and it has a blur effect. On one screenshot (unrendered) you can see the white outline, which should not be there. And on the other screenshot (rendered) you can see how it's supposed to look.