I have the same issue. I don't want to uninstall groupy, but I do have it running, and I'm seeing the freeze. Until today it only froze sometimes, but it's already done so three times today--the last time within a minute of rebooting.
Also, it seems to require a click on the taskbar somewhere before it hangs.
This is a dealbreaker for me: the whole reason I bought Start11 was to able to configure the taskbar the same way I had it on Win10. If I can't do that, I'll go back to OpenShell, which has many more settings for the menu part (although I don't use most of them ).
Still, Start11 other than this issue, is just fine.