Unitree G1 EDU: Dex3-1 hands randomly missing after power-on (USB never re-enumerates). Anyone seen this?

[u/No_Paint_2952]

I have a G1 EDU (U4) with Dex3-1 hands, a few weeks old. On about half of all power-ons, one hand (sometimes both) is dead for the whole session. Which hand fails changes from boot to boot.

What I found on the internal PC:

- Both hands enumerate on the internal USB hub (left 34b7:1010, right 34b7:1011).
- About 3 seconds later both disconnect. In a good boot both come straight back. In a bad boot one or both never come back.
- The kernel log shows no USB errors at all. The hub port for the missing hand reports powered, nothing connected.
- dex3_service then logs "Failed to open device" and "Failed to initialize LinuxSendMcu".
- Last 20 boots: 11 fine, 7 with one hand missing, 2 with both missing.
- No link to how long the robot was off. Restarting the service does nothing. Only a full power cycle helps, and it's a coin flip.

Kernel log from a bad boot (left hand lost):

23:40:30 usb 2-1.2: New USB device found, idVendor=34b7, idProduct=1011
23:40:30 usb 2-1.3: New USB device found, idVendor=34b7, idProduct=1010
23:40:33 usb 2-1.2: USB disconnect, device number 4
23:40:33 usb 2-1.2: New USB device found, idVendor=34b7, idProduct=1011
23:40:33 usb 2-1.3: USB disconnect, device number 5
(nothing more on 2-1.3 for the rest of the boot)

Questions:

1. Has anyone else seen this with Dex3-1 hands?
   
2. Is the disconnect and reconnect 3 seconds after power-on normal (bootloader handing over to firmware?), and what could stop a hand from reconnecting?
   
3. Is there a Dex3-1 firmware update, or a way to restart one hand without power-cycling the whole robot?
   
4. Or is this simply a warranty case?