HELP AC Outlets blowing devices!

BurbMan wrote:
Interesting stuff! It never occurred to me that a faulty neutral could create voltage fluctuations in a split phase set up like a home or RV but makes perfect sense the way it's explained.

Interested to see if OP can locate the problem, and if so whether it was in the RV or on the supply side.

Previous S&B house in NY had a 12/3 running from the main panel to the 2FL where it split into two 15A bedroom circuits with a shared neutral. Was AL wire to boot!

Found this from a Square D tech bulletin, note second bullet:

There are several significant disadvantages to be found in the practice of
sharing neutrals:
• On two-pole common-trip circuit breakers, both circuits are interrupted
during any type of fault. If a shared neutral circuit feeds many rooms,
then all rooms lose power if a fault occurs in any one room. If a shared
neutral circuit feeds receptacles and lights, both will lose power with a
fault on either one.
• If the homerun neutral is lost, the connected loads are subject to
voltages varying from 0 V to 240 V (line-to-line). The likely result
from this is severe damage to any connected devices due to extreme
under- and over-voltage conditions.
• On two-pole independent-trip circuit breakers, one may find hot wires
in a junction box that was presumed dead. One cannot overemphasize
how dangerous this would be. If one of the shared neutral circuits were to
trip due to a short-circuit or overload, the other circuit would remain hot.
Anyone servicing any device in that junction box may be exposed to
live conductors.

The NEC still allows shared neutral circuits, but I believe it now requires them to be on a common-trip double breaker to avoid the hazard identified in the 3rd bullet above.