Notes audio recording exports only 42 s instead of 35 min

Device & software

• iPhone 16 Pro (256 GB)

• iOS 18.4.1

• iCloud sync enabled

Issue

1. Used Notes ► New Audio to record a voice conversation (≈ 35 min).
2. Playback inside Notes shows the full 35 min and works fine.
3. Share ► Save to Files / AirDrop / Mail exports a 350 KB .m4a that plays only 42 s.
4. Repeating the export, force-quitting Notes, and rebooting the phone doesn’t help.

What I’ve tried

• Confirmed there’s > 15 GB free storage.
• Left the note open on Wi-Fi until end-to-end playback completed.
• Duplicated the recording inside Notes (duplicate has the same problem).
• Tested Voice Memos – long recordings export correctly there.

It previously worked fine. Any ideas what I could do?