How to reproduce:
1. Open the user's attached project ("FBXExportBugDemo.zip")
2. In the "Project" window go to Assets > Input Mesh folder
3. Right-click on "BaseMale.prefab" and select "Convert to FBX Prefab Variant"
4. When the prefab gets converted to FBX drag it to the Hierarchy
5. Notice weird eyes of the model

Expected results: No scale is applied to the Z-axis when it's exported as FBX and placed into the scene
Actual results: A submesh of the model is scaled when it's exported as FBX and placed into the scene

Reproducible with: FBX Exporter 3.2.0-preview.2, 4.0.0-pre.1 ( 2019.4.18f1, 2020.2.3f1, 2021.1.0b3, 2021.2.0a3)
Not reproducible with: 3.1.0-preview.1 (2019.4.18f1, 2020.2.3f1, 2021.1.0b3, 2021.2.0a3)
Couldn't test with: 2018.4.31f1 (Errors downgrading)