After Effects 26.3.0 + Media Encoder 26.3.1 fail to export projects stored on SMB NAS unless Media Encoder is started first after reboot

Title

After Effects 26.3.0 + Media Encoder 26.3.1 fail to export projects stored on SMB NAS unless Media Encoder is started first after reboot

System Information

• Mac Studio M2 Max
• 64 GB RAM
• macOS Sequoia 15.7.7
• After Effects 26.3.0
• Media Encoder 26.3.1

Issue

Since updating to After Effects 26.3.0 and Media Encoder 26.3.1, exporting an After Effects composition to Media Encoder fails consistently when the project is stored on an SMB network share (NAS).

The exact same workflow worked correctly before updating.

Projects stored on the internal SSD export normally.

Steps to reproduce

1. Restart the Mac.
2. Open After Effects first.
3. Open a project located on an SMB NAS.
4. Send a composition to Media Encoder.
5. Start encoding.

Actual result

Media Encoder immediately fails with:

"Output could not be created. Check whether the output is write-protected or locked."

Sometimes the log also reports that the temporary After Effects project cannot be read.

Workaround

After every Mac restart:

1. Start Media Encoder first.
2. Clear the Media Cache.
3. Leave Media Encoder running.
4. Start After Effects.
5. Export works normally.

If After Effects is started first, clearing the Media Cache afterwards does not solve the issue. The Mac must be restarted again.

Additional information

• Projects located on the internal SSD do not show this problem.
• The issue only occurs with projects stored on our SMB NAS.
• This workflow has been used successfully for a long time and only started failing after updating to AE 26.3.0 / AME 26.3.1.
• The problem is fully reproducible.