Cannot trim clips when “Enable Mercury Transmit” is active — macOS M3 Max

Hi, I’ve found a consistent issue in the latest Premiere Pro Beta version.

When “Enable Mercury Transmit” is turned on (to preview the timeline on an external monitor), I can’t trim clips normally by dragging their edges in the timeline.

• The clip only shortens or extends a few frames at a time, and then stops.

• I have to release and drag again repeatedly to make any further change.

• As soon as I disable Mercury Transmit, trimming works perfectly again.

This happens with all clips, even those without effects, proxies, or AI enhancements.

Steps to reproduce:

1. Enable Mercury Transmit and choose an external monitor.

2. Try trimming a clip in the timeline.

3. The trim operation becomes laggy or unresponsive.

4. Disable Mercury Transmit → trimming works normally.

System Info:

• macOS 15.2 (24C5022e) — or replace with your exact OS version

• MacBook Pro (M3 Max, 16 cores, 32 GB RAM)

• Premiere Pro Beta (include your build number here)

• External monitor connected via HDMI/Thunderbolt

Expected behavior:

Trimming should work smoothly even when Mercury Transmit is active.

Actual behavior:

Trimming is limited to small frame increments and stops responding until Mercury Transmit is disabled.

Thanks for looking into this — it’s 100% reproducible on my system.