There are several things it might be.. One of my favorite lines is that many RVers have a few screws loose.. In your power distribution panel there is a circuit breaker that powers these devices. (or it may be on a sub panel or on an inverter, mine is in a sub panel which is not in the same place as the primary panel)
One of the screws in my Primary took over 2 full turns before I felt resistance.. The wire was very loose and did not always make contact.
Then the power may run though one or more junction boxes or other outlets.. And again we have the potential for bad connections.
And wires sometimes break.