smartmontools shows nothing concerning and total bytes written = 0.172373 TiB (well below the drive's expected useful life).
No reboots for over 12 hours, which is a record since this issue came to my attention
![Smiley :)](https://forum.tinycorelinux.net/Smileys/default/smiley.gif)
The only difference between current setup and the previous iteration (which did have an unexpected reboot) is the TCL downgrade to version 12.
I'm chalking this up to a linux kernel regression between 5.10.3 and 5.15.10 that affects this specific use case (wireless router with multiple wireless interfaces). But with the other small changes between TCL versions it's hard to definitively exclude some other possibility.
Topic may be marked as solved. If I have bad news (another unexpected reboot) or good news (a week or more without unexpected reboots), I'll let you all know.
You are a sharp and generous bunch. Thank you very much for all your help.
P.S. CNK, in one of the several iterations of my setup I did change the wireless USB adapters to different ones with identical chipset (Ralink RT5370) and the issue recurred. So it was not a hardware problem with the adapters.