Prefab becomes corrupted upon importing of Standard Assets from the asset store.

Repro steps:
1. Open attached project.
2. In the project folder, click on Prefabs and select the Explosion prefab.
3. Make sure Explosion prefab works (i.e. you can view it in the inspector, drag it in the scene and preview the effect, etc.)
4. Go to asset store and download Unity's Standard Assets (http://u3d.as/1Fm)
5. Import Standard Assets after they have finished downloading.
6. Select Explosion prefab in the Project folder and see if it's working.
7. If it's still working, restart Unity and select the Explosion prefab again. It's corrupted (see image CorruptedPrefab_1.jpg) and warnings appear in the Inspector (see CorruptedPrefab_Errors.jpg).

Expected outcome: prefab to not be corrupted.

Notes:
- once corrupted, even if everything is deleted in the project folder, the library, and Unity is restarted, upon importing the Explosion prefab (attached Explosions.unitypackage) it would still appear corrupted.
- sometimes the corrupt object appears with two transforms (see CorruptedPrefab_TwoTransforms.jpg)
- Issue does not appear in 5.4.0b2-4
- Reimporting the custom package in 5.4.0b2-4 (possibly lower) fixes the prefab.
- I randomly succeeded with another prefab (a couple of nested primitives, no scripts) becoming corrupted, but it was much harder to reproduce.
- Tested for regressions, issue appears in 5.3.1f1, 5.3.2f1 and latest patch 5.3.2p1.
- Possibly related to an ancient bug which had gotten lost in limbo: http://fogbugz.unity3d.com/default.asp?568536#1066668953