You are probably right about the alarm, it is an indicator of low battery.
A monitor could tell you what is happening but won't prevent the various parasitic drains (radio memory, detectors, etc.) that pull the battery down. Probably the best move is to put a battery disconnect switch on the negative wire for when the camper isn't in use. If you keep it at home you could also keep it plugged in.
There is also a Facebook Hummingbird group which is friendly and helpful.