smtpmic(4) wedged?

Most of the milk-v jupiter machines I have start to exhibit the same
behavior after some time:

[...]
smtpmic0: can't read register 0x1d
smtpmic0: can't write register 0x1d
WARNING: can't update clock chip time
smtpmic0: can't read register 0x1d
smtpmic0: can't write register 0x1d
WARNING: can't update clock chip time
etc etc

so the RTC isn't updated hourly, but later at reboot:

smtpmic0: can't read register 0x1d
smtpmic0: can't write register 0x1d
WARNING: can't update clock chip time
syncing disks... done
smtpmic0: can't read register 0x1d
smtpmic0: can't write register 0x1d
WARNING: can't update clock chip time
xhci0: halt timeout
xhci0: halt timeout
xhci0: reset timeout
rebooting...
smtpmic0: can't read register 0x7e
smtpmic0: can't write register 0x7e
reboot failed; spinning

oops.  Looking at the conserver logs I see these messages may appear
1h+ up to 48h+ after boot.  No idea what is going on.

-- 
jca