How to reproduce:
1. Open the attached "1252436 repro" project
2. Copy the content of Assets/HubProduction.prefab and save it for later
3. Open "Prefab" Prefab from the Assets folder
4. Select the "MetalCube" GameObject from the Hierarchy window
5. Disable and enable the "MetalCube" GameObject
6. Save the Prefab
7. Copy the content of Assets/HubProduction.prefab and compare it against the content of the 2nd step
8. Select the "Prefab" Prefab from the Assets folder and press "Tools" > "Resave selected assets"
9. Copy the content of Assets/HubProduction.prefab and compare it against the content of the 7th step

Expected result: the file content hasn't changed since Serialization should not modify prefabs
Actual result: a block of data has been moved to a different place in the file

Reproducible with: 2019.3.0a3, 2019.4.1f1, 2020.1.0b13, 2020.2.0a15
Not reproducible with: 2018.4.23f1, 2019.3.0a2

Notes:
-It's easiest to reproduce this issue by using a Version Control program like GitHub Desktop to track the changes.
-The data being moved to different places in the file is usually Animator's data but it doesn't seem to be exclusively problematic
-The issue isn't exclusive to .fbx format, the same behavior reproduces with .obj and .dae file formats