UI focus bug

This has happened to me on the last 2 versions, but that's all I've used.

Entering play mode the top menu flickers, and most of the ui is unresponsive. It takes clicking a lot to get focus. If I get focus on some areas like the project view or switch from game/scene it gains focus and sticks. If I can register a click on the top menu it reverts to the bad behavior once I close the dropdown. If I can register a click on a hierarchy item it gets focus but the rest keeps flipping back and forth and it slows the UI greatly.

This doesn't always happen, there is some trigger I can't find and once you hit that it happens consistently when entering play mode until you restart Unity. It triggers fairly often for me, 5-10 minutes or so after I open Unity.

It would be great if you could submit a bug report for this issue with a reproducible.

I'm having the same issue. There is no obvious reproduce, the problem seems to occur randomly. The reproduce is basically "use Unity for a while" and at some point the UI is stuck as described above.

What I can bring to the table though: Once the UI is stuck and you select an entry in the Hierarchy, Unity outputs this message:

Should not be capturing when there is a hotcontrol
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr) (at C:/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:179)

I've seen this just a minute ago in Unity 2018.4.22f1.

Seems like there is a strong link to if I have had the profiler open. It's not always an immediate trigger, it doesn't go away when the profiler is closed. But not using the profiler like yesterday I didn't use it all day, and no bug. Today it hit right after opening the profiler for the first time.

Sort of makes sense because it acts like a window focus issue, which implies something else is trying to take it.