System info     Application: Premiere Pro (Beta) v27.0.0.32     OS: Windows v10.0.26200, RAM: 63,77 GB GB, CPUs (logical): 32

Exporting MP4 exports video and audio separately and doesn’t merge them when export’s finished.
 

n the latest version, 27.0.0 build 32, this no longer happens when exporting from Premiere, but it still happens when exporting from the encoder.

I'm also having this other problem

Summary: Final program export loses one audio channel (stereo collapses to mono/single-channel) in Premiere Pro Beta, regardless of export format.

Description: When exporting the sequence "Final multicam" directly from the Timeline, the resulting video file only contains audio in one channel. This happens consistently across multiple export formats (tested with H.264/MP4 and MOV/QuickTime), ruling out a codec- or preset-specific cause.

Verified NOT the cause:

• Sequence audio track (Audio 1, 4 clips) was inspected: Volume levels are correct and identical across all clips, no clips are muted.
• Channel Volume (source-to-stereo mixdown) parameters show identical Left/Right values on every clip — the panning/mix is symmetric and correct.
• Exporting the audio alone as a separate WAV file produces correct, fully stereo audio.

Conclusion: The sequence and its audio mix are correct. The channel loss occurs specifically during video export/rendering (audio muxed into the video container), not in the timeline or source media.

Environment: Premiere Pro (Beta build)

Steps to reproduce:

1. Open sequence with stereo audio mix confirmed correct (verified via standalone WAV export).
2. Export to video (tested: H.264/MP4, MOV) using "Match Source" or other presets.
3. Play back exported file — audio present in only one channel.
4. Change export format — same result persists.

Expected result: Exported video retains full stereo audio matching the standalone WAV export. Actual result: Exported video audio collapses to a single channel.