[OSX 10.13][Unity 5.6] Hierarchy becomes blank when switching between hierarchy and scene tabs while in play mode

To reproduce:
1. Open attached project
2. Play scene
3. Switch from hierarchy to scene multiple times

Expected vs Actual: hierarchy window should not become blank

Workaround: click again on hierarchy tab or exit play mode

Reproducible: 5.6.2p3, 5.6.3p1, 5.6.3p4
Not reproducible: 5.5.4p1, 2017.1.1p3, 2017.2.0f1, 2017.3.0b2

Note: issue reproduces easier with higher CPU and RAM usage (easily reproduces when there are only 1GB free of RAM)