My Cloud Mirror inaccessible

A little while ago my MyCloud Mirror became inaccessible: Its UPnP service disappeared from the devices on which it used to be visible, and I’m no longer able to access its dashboard.
I am still able to ping the machine, and the three LEDs are still steady blue.

Is there a way to recover / repair the device ? (I haven’t yet tried to remove the two disks but I assume the data are still there and valid.)

For example, is there a way to log onto the device to try to repair whatever Linux services are responsible for servicing the dashboard and UPnP interfaces ? (In the worst case I could even try to re-install a Linux distribution, so long as I don’t have to touch the data on the two disks…)

Thanks for any help !