This early morning, after a sleepless night, having left my Rossini disconnected from the grid, just to give it one more try, I reconnected it and flipped it back on.
To my big surprise it just started up normally. I felt relieved. And played some music. After about 15 minutes it crashed again, music stopped and the green lines reappeared on the display.
I managed to download the system logs before the second crash.
It does not respond to whatever front panel button, and @andrewt Mosaic cannot find or access it, nor can I connect from its IP address.