Microsoft bug report pointed to nimbus.exe having caused the kill of svchost.exe hosting RPCSS (Svchost.exe -k RPCSS).
This event triggered an unexpected reboot of the server. Apart from Microsoft Defender, there is no Antivirus running on this system.
Microsoft identified "nimbus.exe" caused the service kill, and consequent server reboot.
The following robot update addresses the issue:
robot update 9.39T1 (robot_update-9.39-DE563663-20230719.133817-1.zip)
The subsequent GA Version of the robot, e.g., 9.40, will include the code change present in 9.39T1.
robot update 9.39T1 is attached to this KB Article.