Well, maybe not a crash, just skipped a tooth or two in the timing belt.
I had "About phone" -> "SIM status (SIM slot 2)" and watching the abysmal signal strength, -121 dBm 23 ASU.
A regular daily alarm popped up and began the raucous noise so I tapped "Dismiss" and the notification visually went away. Not so much for the noise. I had previously set the volume buttons to dismiss alarms so tried both up and down -- noise continued.
Interesting the buttons were reversed. The top button (next to "start") displayed the slider going down. The lower button the opposite. Still full noise and the up/down buttons made no difference to the noise level.
I could not leave the current screen until after the noise had run it's term.
Now the thing seems fine. I have not yet done a cold-start as there is another alarm due in a while so will see what's what for that. I will leave it on the "Sim status" page.