[Bug]: M4B encode canceled automatically

[Gsam33]

What happened?

I started a m4b encode, wich was instantly stopped by the system. But the UI stioll shows that its in progress.
Only happens with a specific book.

What did you expect to happen?

Encode should proceed or at least the system should tell me it has been canceled and why.

Steps to reproduce the issue

Not sure how to on other systems. Can provide book for testing purposes.

Audiobookshelf version

2.36.0

How are you running audiobookshelf?

Docker

What OS is your Audiobookshelf server hosted from?

Other (list in "Additional Notes" box)

If the issue is being seen in the UI, what browsers are you seeing the problem on?

Chrome

Logs

2026-08-20 16:55:06.225210+00:00[2026-08-20 18:55:06.225] INFO: [ToolsController] encodeM4b: Starting audiobook merge for "Die richtig große Märchen-Box" with options: {"codec":"copy","bitrate":"128k","channels":"2"}
2026-08-20 16:55:06.227273+00:00[2026-08-20 18:55:06.227] INFO: Start m4b encode for 2350cc50-ebfb-412e-890d-13a87cb27f50 - TaskId: 6155b4f3-4162-4a48-aeff-e4999d40e180
2026-08-20 16:55:06.231372+00:00[2026-08-20 18:55:06.231] DEBUG: [ffmpegHelpers] Wrote /metadata/cache/items/2350cc50-ebfb-412e-890d-13a87cb27f50/ffmetadata.txt
2026-08-20 16:55:06.447737+00:00[2026-08-20 18:55:06.447] DEBUG: [ffmpegHelpers] Merge Audio Files ffmpeg command: ffmpeg -f mp4 -i /audiobooks/Hans Christian Andersen/Die richtig große Märchen-Box B0DP9KT74Q GER/Die richtig große Märchen-Box B0DP9KT74Q GER.m4b -y -f mp4 -map 0:a -acodec copy -ac 2 -b:a 128k /metadata/cache/items/2350cc50-ebfb-412e-890d-13a87cb27f50/Die richtig große Märchen-Box B0DP9KT74Q GER.m4b
2026-08-20 16:55:07.074267+00:00[2026-08-20 18:55:07.074] INFO: [ffmpegHelpers] Merge Audio Files Killed by User
2026-08-20 16:55:07.074644+00:00[2026-08-20 18:55:07.074] INFO: [AbMergeManager] Task cancelled 6155b4f3-4162-4a48-aeff-e4999d40e180

Additional Notes

TRUENAS Community Edition

Book ffmped probe:
{
"error": {}
}