About 20:00 last night, SPN1.near died. The mote was in a mode of resetting every 10 seconds, which didn't change in response to "rxb" or "xs" commands.
~10:45 Found that the DIN connector to the SPN1 was slightly pulled out. Reseated, cycled power on mote, and now works. Also measured voltage to SPN1 at 17.1V -- should be high enough! (I note that logged voltages are steadily dropping -- now at 15.3.)