After installing Start11, all the icons on the taskbar of the second monitor went invisible:

and sometimes even disappear:

I've read that this is a common Windows 11 bug, but that should've been patched around 2021. I'm currently using the latest Windows 11 Enterprise, version: 21H2, build: 22000.918; with the latest updates installed.

Furthermore, I'm using 2x HP 25X monitors with a resolution of 1920x1080. Both monitors are connected with displayport cables.
When the icons in the taskbar of the second monitor are invisible, I can click on the empty space, and the app that is located on that position will open. But because I can't see the icon, I don't know what I'm clicking on. If I turn off the setting “Show taskbar on all monitors” in the Windows settings, and turn it back on, the icons will show for a moment. But then they will disappear again, almost immediately.
This setting can be found in Windows settings > Personal settings > Taskbar > Show taskbar on all monitors.
I've got this issue on multiple systems. Is this a known issue, and is there a fix for it?