I’m using and external SSD that is connected over USB. At the beginning there was no problem with rebooting, but I can’t tell wenn it startet, as I usually reboot only when there is a new version.
I wonder if perhaps there’s something that’s enabled a USB sleep state that wasn’t previously on. I have a specific USB 3.0 SATA enclosure that likes to doze off under Windows if it hasn’t received write traffic in ~5 minutes or so, but it’s perfectly well behaved under Linux.
Does this happen on every reboot, even if the system was just started?
Assuming it does happen every time, or you can determine “about how long it takes” to trigger it - see if you can gather the contents of the dmesg log before triggering a reboot and see if there’s anything about your USB device disconnecting/sleeping.
Did you ever work out what this was? I’ve just done a clean install of 25.04 and I have the exact same logs on shutdown. Running under Proxmox on somewhat old hardware: supermicro X11SCL-F with an E-2136.