If none of the previous poster items are the culprit, it may be your power monitor/protection device (if equipped) such as a Progressive Dynamics surge and voltage protection unit. If your shore power is producing random surges or brown out (low voltage) conditions, the power monitor device should disconnect your coach from shore until voltage conditions test in the normal range again; at which point it should reconnect to shore power again automatically.
The power monitor should (may) show a fault code when it trips off, which would confirm a shore power fault sense issue has caused the monitor to trip off. I know the Progressive Dynamics units also allow you to bypass protection sense to enable continuous connection to shore, but make sure you are running non voltage sensitive loads only if you do that (nothing with a motor for sure).
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