To reproduce:
1. Open user's attached project
2. Open scene "Main"
3. Play the scene and pause it after a few seconds
4. Open Profiler, add Memory profiler and switch to detailed view
5. Take a memory sample, expand scene memory list

Expected result: The amount of "PhysicMaterial" is the same as "BoxColider"
Actual result: There are a lot more "PhysicsMaterial" than "BoxColider"

Reproduced with: 5.6.5p1, 2017.1.3f1, 2017.2.1p2, 2017.3.0p3, 2018.1.0b4

Notes:
- The amount of PhysicsMaterial is getting higher and higher even though the error
"Could not create Material. Maybe you have too many materials in your scene. Only 65535 are allowed." is displayed.