As soon as I read your title I thought it might be this bug. I get it maybe a few times per month in Windows 7. I have not seen it happen in Windows 10. You can

As soon as I read your title I thought it might be this bug. I get it maybe a few times per month in Windows 7. I have not seen it happen in Windows 10. You can fix it without rebooting or killing explorer.exe by shift+right-clicking on the taskbar item.