Neighbor complained of 120v window A/C not working and dim lamps on same circuit in old mobile home. Check of circuit revealed 82v on 120v circuit. Further check of incoming line showed 82v on one leg of service in breaker box (resulting in 82v on the affected bus bar). Disconnect box at service pole, however, checked 120v on both legs going out to house.There is one connection in the line under the mobile home between the service entrance cable and the pigtail coming from the breaker box. Could a deteriorating connection or other wire compromise be the possible cause of decreased voltage or possibly a compromise of the bond or ungrounded conductor?

Loose Wire, or connection for sure, Not Just the hots, But a loose Neutral is more dangerous, and possible. May be where breaker plugs onto.