Bug Report: Substance 3D Painter 12.1.2 — Export Fails to Network (Synology SMB) Drives

Summary

Exporting texture maps in Substance 3D Painter 12.1.2 fails when the export destination is a mapped network drive pointing to a Synology NAS share. The export process reaches the "Finalizing export" stage and then fails for every map in the batch simultaneously. The issue does not occur when exporting to a local disk or to a mapped drive on a QNAP NAS. Rolling the application back to 12.1.1 resolves the issue completely with no other changes to the system.

This strongly indicates a regression introduced in the 12.1.2 release affecting how the exporter finalizes (writes/renames) files on certain network/SMB destinations.

Environment

• Application: Substance 3D Painter
• Affected version: 12.1.2 (issue present)
• Working version: 12.1.1 (issue not present — confirmed by rollback)
• OS: Windows 11, version 25H2 (identical build on both test machines, same update history)
• Export destination: mapped network drive (drive letter), Synology NAS share via SMB
• Issue reproduced on two separate Synology NAS units
• Export to a local disk: works fine
• Export to a mapped drive on a QNAP NAS: works fine (same PC, same session)

Steps to Reproduce

1. On a Windows 11 PC running Substance 3D Painter 12.1.2, open a project and set the export destination to a mapped network drive pointing to a Synology NAS SMB share.
2. Run "Export Textures" (Stacks/Map export) for a standard set of output maps (e.g. albedo, normal, roughness, displacement, in both "high" and "mid" bake variants, plus a "clean" pass).
3. Observe the export progress through to the "Finalizing export…" stage.

Expected Result

All exported maps write successfully to the destination folder on the Synology share, as they do on version 12.1.1 and as they do when exporting to a local disk or a QNAP-hosted mapped drive.

Actual Result

The export dialog shows:

Finalizing export...
Error during the export (see logs)
Failed to export:
normal.png
displacement_high.png
displacement_mid.png
albedo.png
normal_mid.png
normal_high.png
roughness.png
clean.png

Every map in the batch fails at the same "Finalizing export" step (not partway through individual bakes), suggesting the failure is in a shared finalize/write-to-destination routine rather than in per-map processing.

Log Output

The application log shows only:

[StacksExporter] Map export ended

No further detail, error code, or underlying Windows/I-O error is surfaced in the log, which made this difficult to diagnose from the application side alone.

Diagnostic Steps Taken (ruling out non-application causes)

Before concluding this was an application-level regression, the following were tested and eliminated as causes:

• Not a NAS-side/permissions issue: a second Windows 11 PC on the same network, still running Painter 12.1.1, exports successfully to the exact same Synology destinations at the same time.
• Not a credential issue: cleared and re-entered cached credentials (Windows Credential Manager) for the Synology connections on the affected PC — issue persisted while still on 12.1.2.
• Not an SMB client configuration difference: Get-SmbClientConfiguration output compared between the affected PC and the working PC — identical relevant settings (including RequireSecuritySignature, EnableInsecureGuestLogons).
• Not an NTLM policy difference: "Network security: Restrict NTLM: Outgoing NTLM traffic to remote servers" is set to "Not Defined" on both machines.
• Not a Windows Update difference: Windows Update history compared between both machines — identical KBs installed on identical dates on both PCs.
• Not network/drive-mapping specific: the same affected PC exports without issue to a different mapped network drive (QNAP NAS) and to local disk, using the same Painter version, in the same session.

Root Cause Isolation

With all environmental, network, and permission variables controlled for and ruled out, Substance 3D Painter was rolled back from 12.1.2 to 12.1.1 on the affected PC via the Creative Cloud desktop app's "Other Versions" option, with no other changes made. Exporting the same project to the same Synology destination immediately succeeded after the rollback. This isolates the regression specifically to the 12.1.2 build.

Request

Could you confirm whether a change in 12.1.2 affected the map/stacks export finalization routine for network (SMB) destinations, particularly around Synology NAS shares? Happy to provide the full log file, a Process Monitor capture of the failing write/finalize operation, or further reproduction details if useful.