Reproduction steps:

1. Run Cache Server
2. Create a New Project
3. "Editor" -> "Preferences" -> "Cache Server"
4. "Cache Server Mode" -> "Remote"
5. "IP Adress" -> "127.0.0.1"
6. Check Connection
7. Exit Editor
8. Go to "C:\ProgramData\Unity\cache\packages\packages.unity.com\com.unity.purchasing@2.0.1"
9. Delete all the ".meta" files
10. Create a New Project
11. Once loaded, focus on another window
12. Re-focus on the Editor

Expected Result: The Editor regains focus and you can continue your work
Actual Result: The Editor enters an 'infinite loop' and you have to Force Close it (Sometimes results in an error)

Reproduced with: 2018.2.0a6, 2018.2.0a1
Did not reproduce on: 2018.1.0b12, 2017.4.0f1, 2017.3.2f1