What happened:

For some projects, when downloading a small update (like an added folder or edited prefab/script), the Editor freezes for several minutes on 100% instead of finishing right away. After waiting 4-10 minutes, Collab finally finishes and starts to import changes. This issue repros on Windows 10 machines, not on OSX.

Does not repro with new, empty projects.

Repro Steps:

1. Download test project onto two locations, one of them a Windows 10 machine and the other either on the same machine or a different one running on any OS.
2. Open both projects, edit a prefab's transform on the non-Windows 10 instance, save changes and then Publish them.
3. On the Windows 10 project instance, Update to get the latest change.

Expected: Update finishes shortly after reaching 100% and Editor becomes usable.
Actual: Collab Toolbar freezes at either 0% or 100% of progress, Editor freezes for between 1-4 minutes before resuming normal operation.

Workaround: Oddly enough, using Collab History to Restore to an earlier commit and then going back to the latest version allows updates to finish as expected until the Editor restarts.