Focusing the Editor causes a two seconds freeze with the project attached to Case 1108597 on my PC. Looking at the Profiler reveals it's caused by AssetDatabase.V2.Scan. It probably gets worse the more assets the project contains. Spoiler: Profiler Screenshot Reproduce Use hardware similar to the PC I submitted the bug-report with. You probably can't reproduce it on high-end hardware. Open project from Case 1108597 Open Notepad Focus Unity Editor Repeat step 3 and 4 as often as you want. Actual Focusing Unity Editor displays for about two seconds a "Waiting Mousecursor" before the editor gets responsive. Expected Editor should be responsive immediately.