Animation clips are updated properly in the importer when updating an FBX file containing additional clips, but if you change an option, example Loop option, before updating the FBX file, the new clips are not added to the list. The new clip(s) are added the the FBX file and can be manually added to the model importer list, but should be automatically added, exactly like when you don’t change options (like Loop) in which case you get the expected result with the new clip added automatically.

Reproduction steps:
1. Open the attached project "ReproProj"
2. In the Project window, create a folder called "subfolder" and open it
3. Extract the attached "FBX.zip"
4. In "FBX/FBX" folder, find the "ArmatureObject.fbx"
5. Import that into "subfolder"
6. In the Project window, select the "ArmatureObject.fbx"
7. In Inspector, tick the "Loop Time"
8. Right-click the Project window
9. Select Show in Explorer
10. Change the "ArmatureObject.fbx" in "subfolder" with ArmatureObject.fbx" from "FBX/FBX/update/"
11. In the Project window, select "ArmatureObject.fbx"
12. In Inspector, observe the "Clips" section

Expected result: 4 clips exist
Actual result: 3 clips are present

Reproducible with: 6000.0.64f1, 6000.3.2f1, 6000.4.0b2, 6000.5.0a3

Testing environment: Windows 10 Enterprise 21H2
Not reproducible on: No other environment tested

Note:
- "Source Take" drop-down contains new animations