How to reproduce it:
1. Open the attached project "1309068.zip"
2. Load the "SampleScene" Scene
3. Select a "GameObject" in the Hierarchy Window
4. In the Inspector Window expand the "Localized String" foldout
5. Observe the foldout below of the "Preview Arguments"

Expected result: Foldout "Other properties" is visible with no error messages
Actual result: "Other properties" foldout disappears and error "You can't nest Foldout Headers, end with EndHeaderFoldoutGroup." appears

Reproducible with: 0.10.0-preview (2019.4.21f1, 2020.2.6f1, 2021.1.0b9, 2021.2.0a7)
Could not test with: 0.3.1-preview (2018.4.29f1) - due to errors

Note:
- In 2018.4.29f1 (0.3.1-preview) error "CS0246: The type or namespace name 'LocalizedString' could not be found (are you missing a using directive or an assembly reference?)" appears

Workaround: Add EditorGUI.EndFoldoutHeaderGroup() before other EditorGUI.BeginFoldoutHeaderGroup()