False failure warning when returning from Topaz Photo

Description of Issue
When I send a photo from Lightroom Classic to Topaz Photo and return it to Lightroom, Lightroom Classic sometimes shows this warning:

“Topaz Photo either failed to start or did not finish successfully. Exit code: 3221225477”

However, the image is usually processed correctly and returned to Lightroom with the edits applied.

The issue appears to be intermittent. It happens when Topaz Photo is using the GPU. If I set Topaz Photo’s AI Processor to CPU, the warning does not appear.

I also observed that system RAM and GPU memory were well below full usage at the time of the warning, so this does not appear to be a simple out-of-memory condition.

Lightroom Classic Version Number (Help > System Info…)
Lightroom Classic 15.2.1 Release
Camera Raw 18.2.2

OS Version Number
Windows 10 Pro 22H2
OS Build 19045

Camera Model (sometimes necessary)
Not camera-specific.
Tested with an existing image in Lightroom Classic during external editing to Topaz Photo.

Step-by-step Reproduction Instructions (in precise terms, please)

1. Open Lightroom Classic 15.2.1
2. Select an image in the Library or Develop module
3. Send the image to Topaz Photo using the normal external editing/plugin workflow (File>Plug-in Extra>Topaz Photo AI)
4. In Topaz Photo 1.4.1, ensure the AI Processor is set to GPU
5. Apply an adjustment and save/return the image to Lightroom Classic
6. Lightroom Classic sometimes displays this warning:
   “Topaz Photo either failed to start or did not finish successfully. Exit code: 3221225477”

Additional observations:
7. If Topaz Photo AI Processor is set to CPU, the problem does not occur
8. If GPU is enabled, the problem is intermittent rather than constant

The Expected Result
If the image is processed and returned successfully from Topaz Photo, Lightroom Classic should accept the returned file without displaying an error.

The Actual Result
Lightroom Classic sometimes displays the warning message above, even though the image has been processed correctly and returned to Lightroom with the edits applied.

Additional diagnostic observations:

• GPU: NVIDIA GeForce RTX 2060, 6 GB VRAM
• NVIDIA Studio Driver: 595.79
• At the time of one warning, Task Manager showed approximately:
  • System RAM: 12.1 / 63.9 GB used
  • Dedicated GPU memory: 3.4 / 6.0 GB
  • Shared GPU memory: 0.5 / 32.0 GB
  • GPU temperature: 38°C
• Windows Reliability Monitor also recorded a LiveKernelEvent 144 during testing

Topaz support reviewed my testing and agreed this does not appear to be straightforward RAM/VRAM exhaustion, and that the behavior may reflect an intermittent GPU/driver + Lightroom interaction.