"The importer reported a generic error" importing Sony FX3 XAVC HS (HEVC 4:2:2) clips with 4-channel audio

SETUP

Premiere Pro 26.5.2

macOS 27.0.1, Apple M4 Pro

Hardware-accelerated decoding: on

FOOTAGE

Camera: Sony ILME-FX3

Format: XAVC HS 4K, HEVC 4:2:2 10-bit, 3840x2160, 59.94p, about 200 Mbps

Audio: 4 mono LPCM tracks, 24-bit, 48 kHz (camera set to 4 audio channels)

Container: .MP4 straight from the camera. Files are complete and play in QuickTime and ffmpeg.

STEPS TO REPRODUCE

1. File > Import (or drag in) any of the FX3 clips.

2. Premiere shows "File Import Failure: The importer reported a generic error."

WHAT I TESTED (all with the same source clip)

- Original .MP4, HEVC + 4 audio tracks: FAILS

- Video track only, copied losslessly into a .mov: IMPORTS

- HEVC + 1 audio track (3-second test): IMPORTS

- HEVC + all 4 audio tracks converted to 24-bit little-endian PCM in a .mov: FAILS

- Sony FX30 XAVC S clips (H.264 4:2:2 10-bit) with the same 4 x 24-bit audio tracks: IMPORT FINE

EXPECTED

FX3 XAVC HS clips with 4-channel audio import like XAVC S clips do.

ACTUAL

Import fails with a generic error. The only workaround I found is removing the audio.

This looks like the same issue as the DJI Osmo Pocket 4 Pro report ("Premiere Pro 26.5.2 fails to import DJI Osmo Pocket 4 Pro MP4 with two stereo audio streams"): HEVC video plus multiple audio streams, so it affects Sony XAVC HS too.