Likely situation is a rusted out wire in the feed. Are the underground wires aluminum, which could rust out not so slowly if the insulation had biodegraded and cracked.
May be at the same place where you made the splice but not guaranteed.
The rusted out remains mixed with dirt could sizzle and change resistance from minute to minute or second to second as you have your meter or a load connected thus you might see a variation in voltage before your eyes.
May be at the same place where you made the splice but not guaranteed.
The rusted out remains mixed with dirt could sizzle and change resistance from minute to minute or second to second as you have your meter or a load connected thus you might see a variation in voltage before your eyes.