I put the number 1 battery on a charger here at the house... and after taking it off the charger and checking it about 8 hours later, both batts showed 12.69 volts. Now 24 hours later, batt 1 shows 12.72 volts, batt 2 shows 12.66 volts. Both have been off charger, and in the same environment, and are measured with the same meter. .06 Volt difference. So the battery that I thought was a problem, actually showed a RISE in voltage over time.

I will load test this evening.

I suspect the real culprit is the loose connection I found... I'll use lock washers on this when I put it all back together.