Editor stops responding when generating previews that involve a scene imported from blender.

### Tested versions

- Reproducible in: 4.3.beta1.mono and dev-5
- Project fails to start in 4.2.2 or older.

### System information

- Windows 10 - Godot 4.3.beta1.mono - Compatibility - GPU: FirePro v4900, dedicated - CPU: Intel Xeon 2.9Ghz, 8 cores

### Issue description


When opening a scene with an animation player imported from Blender. The editor freezes during the preview generation. Truth be told i haven't been able to pinpoint WHAT is causing this. I've been at it for hours and the conditions seem to keep changing or at least are inconsistent. But the setup in the MRP is what causes it the most often.

### Steps to reproduce

- Open a scene imported from blender.
- Save to cause a refresh of previews.
- Editor freezes.

### Minimal reproduction project (MRP)

[mrp.zip](https://github.com/user-attachments/files/15858803/mrp.zip)

Start with the attached MRP and reproduce the freeze by opening the Blender-imported scene and saving to trigger preview generation. Trace the editor's preview-generation path and compare behavior across the listed Godot versions; done means the editor remains responsive for this project and the regression is covered by a reliable reproduction or test.

Written by the indexing model from the issue text.