Is the start menu accessible when the "windows icon" button on the keyboard is pressed?
The reason I ask is becasue it's worth identifying if it's an issue with the GUI or the function of the start menu appearing itself, so by pressing the start button on the keyboard we can identify that.
Secondly, if an admin account works fine it might be due to it being a different profile - how does it work with another profile with the same permissions?
Thirdly, when this happens, have you tried restarting windows explorer.exe via taskmgr to see if something in the background is causing the taskbar to bug out.
Hopefully you find the issue
