Windows Forms with ElementHost hangs up, when start from Visual Studio 2017 in debug. When start it without VS no problems (same debug, like casual exe). Even empty ElementHost hangs up. Programm totally hangs up.
Also, in test project with only form with ElementHost no hangs up. Sometimes ElementHost not show any content, sometimes all works well for ~1 seconds.
Problem is solved. I had disabled "Enable UI Debugging Tools for XAML" in Debug/General in Debug/Options... I interests, why it works? In small WinForms this glitch doesn't happen with any options