To reproduce:
1. Create a new project on first machine
2. Make 10 Cube prefabs and save the scene
3. Commit changes
4. Download the changes to the second machine
5. Delete the prefabs ant meta files from the Projects Assets folder on second machine (not from the editor)
6. Make a change on all the prefabs on first machine and publish the changes
7. On second machine update the project

Expected result: collaboration tab shows Merge Conflicts
Actual result: Collaboration tab shows 100% and, the circle is not complete and the tab is frozen

Reproduced on: 5.6.0b11 2017.1.0f3 2017.2.0b11 2017.3.0a7
Not reproduced: 5.5.4p4 5.6.0a3 5.6.0b7 5.6.0b9
Regression on: 5.6.0b10

Notes: on 5.6.3p3 these steps produces blank collab tab.

On 2017.2.0b11 second machine updates normally, but on the first machine updating it result in the conflict and collab tab freezes