How to reproduce:
1. Open the attached “IN-137625” project
2. Open the Package Manager (Window -> Package Manager)
3. Select the “Foobar” package
4. Export the mentioned package through the Export button in Package Manager
5. Open the exported package in File explorer and check the size of “Sample~” or try importing it into another project

Actual result: The exported package fails to import on a project
Expected result: The exported package is over 0 kb in size and contains all initial data

Reproducible with: 6000.3.0a5, 6000.3.11f1, 6000.4.1f1, 6000.5.0b1, 6000.6.0a1
Could not test with: 6000.3.0a4 (Export button was introduced in 6000.3.0a5)

Reproducible on: Windows 11
Not reproducible on: Tahoe 26.3.1 (M1 max)