visited site 2 again today from about 1:30 till 3:00 monitoring power (voltage dropped again this morning to about 11.2 v)
swapped out viper power cable.
wiggling the cable brings the voltage back up to 12.7 v, (where it should be), but that's what was happening yesterday as well, and I repaired the original cable at that time. since the voltage dropped again this morning, right about the time the wind started getting brisk, and shaking the tower, i suspect a cold solder joint in the power distribution board. I had an extra cable, so I decided to try that first.
will monitor situation, and if voltage drops again, i will replace either power panel, or more likely, entire DSM so that the offending board/box can be scrutinized in a more friendly environment