How to reproduce: (Not reproducible!)
1. Verify that Visual Studio 2015 or 2017 (or MonoDevelop) is set as your External Script Editor
2. Open ScriptReloadTest scene
3. Use the "Assets/Open C# Project" menu item to open the project in Visual Studio
4. Locate the ScriptReloadTest.cs file in Visual Studio
5. modify the public "m_Test###" integer variable by incrementing the numeric suffix
6. switch back to Unity
7. Observe that Unity recompiles Scripts (spinner appears)
8. Observe that the instance of the ScriptReloadTest MonoBehaviour has changed in the inspector to so that it is displaying the NEW name for the m_Test### member variable
9. repeat steps 5) through 8) many times (usually less than 10 but sometimes as many as a hundred)
10. Observe that at some point Observation 8) fails and that the Unity inspector is displaying the OLD name of the m_Test### variable.

Actual result: When modifying a script Unity will sometimes appear to recompile them (the little spinner appears in the bottom right-hand corner), but when it finishes the assembly isn't actually reloaded and unity continues to run with the old .dll

Regression since 2017.1

https://forum.unity.com/threads/script-changes-dont-compile.486287/

-----------------------------------------
Fixed: 2017.1.1p2, 2017.2.0b11