Hi, we currently have a Trouble Report open on Bookworm for which the workaround is disable Wayland.
https://www.nomachine.com/TR10U11031.
However, our own tests have shown that it happens even when an HDMI screen is attached. So if possible, we would like to debug your device further. Before you try disabling Wayland, could you enable debug and gather some logs? We would need logs from a session to the Raspberry device as headless (no HDMI plugged), and then logs from a session with the screen attached, so one set of logs for each session. For instructions on how to enable debug and gather the logs, please check the instructions here: https://kb.nomachine.com/DT07S00243. Send them to forum[at]nomachine[dot]com. Please use the title of this topic as the subject of your email. Thanks!