I deleted Start11 and reinstalled v1.42, turned on autohide of the taskbar on. Then opened enough windows so that Outlook, Chrome, Edge and Word windows that were opened consolidated under individual icons.
I then moused over the chrome icon and three chrome windows popped up, while the taskbar was still up I moused over Edge, Outlook and Work and none of the open windows appeared . I let the taskbar drop down and then moved the mouse down so that the taskbar reappeared and moused over the word icon and the windows reappeared. However, mousing over the other icons (while the taskbar was still up) did not result in the open windows appearing.
In short you have to make the taskbar go back down for the mouse over to work or shut off auto hide. This is a fairly new development and I am not sure which update caused this bug to appear.
Please fix it - very annoying.