Again, I found something new... It's easier to reproduce if I switch a window. For example, If I open Windows Explorer then open start menu, then minimize the Explorer window then open start menu.... Something like that.
If the focus is on the desktop, I just continuously press the Win Key, it can show the content immediately(not always, but most of the time). If I do something, like open a window, open a browser, restore a explorer window from taskbar, minimize a window, switch a window like from explorer to browser... Then open start menu, it's very easy to show the blank content and need to wait the content be loaded.
