The custom start button flicker has been resolved, but if you don't have an app open or pinned to the taskbar, the default Windows 11 start button is used.
If you hide the start button on Primary monitor, if you don't have an app open or pinned to the taskbar, the default Windows start button is displayed, but does not work. If an app is open or pinned to the taskbar, the start button is hidden.
There seems to be an issue related to whether an app is open or pinned to the taskbar and how the Start button is displayed.
Taskbar on the left.
Windows 11 Pro - 22635.4660; Start11v2 - 2.5.0.0