The task bar hiding problem isn't a Star10 issue for me, but to do with Windows 10 notifications. I had this problem on both my desktop machine and laptop after installing Windows 10, and it seemed to go away for a while after installing Start10 - I thought Start10 had fixed it, but it came back.
On my machines, I finally discovered that the taskbar notifications stop it from hiding - if any of the apps on the taskbar, or in the hidden notification area menu, signal a notification, the taskbar won't hide. But you don't always see notifications, especially if they're on the hidden menu. I've found that by clearing the Action Centre notifications and clicking on every icon to check for notifications, the taskbar will hide again.
By customising the notification area (Taskbar properties -> Notification area -> Customise) and making sure that only the icons I want notifications from are enabled, I don't get the problem so much, and it's easy to find a notifying icon that stops the taskbar hiding.
