I have a HP Desktop and a HP laptop. Both are updated to Windows 10 Pro Creators Update, and the last patch was this June, 13, 2017.
I use the taskbar but with double width (the taskbar is nothing else but a window) and hiding, and it was locked. Since a couple of weeks, whenever I restart or start the PC or the laptop the taskbar is reduced to single width. I have to unlock it to change it back to double width. Since some days, I do not lock it anymore, which apparently helps to keep the double width when restarted rep. started. In most restarts/starts it helps but not always.
I did research about it but cannot find a solution at all. I assume it is some glitch.