[Problem] Strange artifact

[vovodroid]

Is there an existing issue for this?

• [X] I have searched the existing issues

Version

0.20 (Release)

Full version info

[code]
OS: Windows 10 build 19044
Word size of FreeCAD: 64-bit
Version: 2024.123.0.14555 (Git shallow)
Build type: Release
Branch: HEAD
Hash: 0c0f69ad4806682096b51f7669d5f1cb83f9c7d7
Python 3.11.7, Qt 5.15.6, Coin 4.0.1, Vtk 9.2.5, OCC 7.7.2
Locale: English
Installed mods: 
  * Curves 0.6.13
  * ThreadProfile 1.87.0
[/code]

Subproject(s) affected?

None

Problem description

Strange artifact (like a diaphragm) appears

Just open the attached project.

Also exported STEP can't be open in PrusaSlicer (Error is "zero object size").

Anything else?

mount.zip

Code of Conduct

• [X] I agree to follow this project's Code of Conduct