https://discussions.unity.com/t/unity-2017-1-p2-issue-with-guiutility-hotcontrol/673753
Unity 2017.1.p2 Issue with GUIUtility.hotControl - Unity Engine - Unity Discussions
Aug 10, 2017 - It looks like there is an error happening sometimes when setting the hotControl. Should not be capturing when there is a hotcontrol...
unityissueenginediscussions
https://docs.unity3d.com/es/2018.1/ScriptReference/GUIUtility-hotControl.html
GUIUtility-hotControl - Unity Scripting API
The controlID of the current hot control.
unityscriptingapi