Sadly, after several episodes of instability with Start 11 V2, I've switched to StartAllBack, which is a bit less sophisticated, but way more stable for an autohide menu aligned at the top of Windows 11.
The problem is described below:
Start 11 V2 seemed stable after purging it and reinstalling it (on Windows 11, Surface Pro 9). I set the taskbar to align 'top', and set 'enhanced' mode for 'autohide'. It was fine for a few days, then after a Windows update, the taskbar icons on left and right side 'slipped down' so only the top edges were visible on the taskbar.
This taskbar issue persisted after a reboot, so I tried turning off the 'enhanced' mode to stop autohide to see if that would help. To do this, Start 11 requires Windows Explorer to restart. When Windows Explorer restarted, the screen layout kept repeatedly refreshing, making the icons jump. At this point, the start menu was responding normally, so I rebooted, but after reboot the desktop started up in the same display refresh loop and the Start 11 V2 taskbar and menu were unresponsive.
I booted into the Windows boot menu and used Macrium Reflect to restore from a recent system backup, before purging and uninstalling Start 11 V2. This is the third time I've been through this cycle with the same result - the problem always seems to happen after disabling the 'enhanced' taskbar option and restarting Windows Explorer.
I had a similar issue on my Del XPS desktop PC, but after reinstalling Start 11 V2, I left the taskbar unenhanced (no autohide), and so far it's been stable. Unfortunately, on the Surface Pro, I need the extra screen real estate an autohide taskbar provides ¯\_(ツ)_/¯