Steps to reproduce:
1. Open user's attached project.
2. Open the scene called "Test".
3. Select "GameObject" from the hierarchy.
--- Note that it has a component called Script1.
4. Lock the inspector panel.
5. In the project, select Script1 and duplicate it, which will cause a compilation error.
--- Note that the inspector no longer redraws and the error spam in the console.
--- Note that the inspector can no longer be unlocked and the tab cannot be closed.
6. Delete the duplicated script.
--- Note that the inspector returns to life.

Regression introduced in 5.3.4p4