Repro steps:
1. Open "Dungeon Objects" project
2. Observe that Import window disappears while assets import, Unity uses a lot of memory.
Note: Stack trace attached (Editor.log)

Stack trace: _Uninit_move<unsigned char * __ptr64

Actual: Import window disappears when assets load, full project crashes
Expected: The assets load correctly, Unity does not crash

Reproduced on: 5.5.0b1 (Import window freezes on Simplygon.dll), 5.4.0p3, 5.3.6p3
Did not reproduce on: 5.2.4f1