Using the Modern interface in Start11 I have add some issues where I move the icon quickly it disappears. I close the menu and reopen and it's blank. I retry a couple times and then add the app again.
Sometime later I open the menu and the missing icon is there and the additional one.
I am not sure I can recreate it, but it's happened at least 4 times in version 1.0 and 1.01.