LP alarm
If your unit is new and still under warranty, I would recommend taking it back to the dealer for a check over. If your water heater is under the sink and you can get to it I would suggest getting a small bottle of water and high concentration of Joy liquid detergent and spray on the gas lines. Better safe than sorry. If there is a leak in one of the lines the soap will bubble indicating where it is. Naturally, you will want to put a towel or something under it to catch the overspray.
I have a Southwind motorhome and the other day I was looking at the "Smoke Alarm" mounted on the bedroom wall. Surprise, Surprise, it turned out to be a Carbon Monoxide detector. Being a volunteer fireman and working as a health and safety inspector for General Motors Corporation for a number of years, I know that Carbon Monoxide detectors are supposed to be mounted near the floor. Carbon Monoxide, like propane gas, is heavier than air and goes to the lowest level. That means that by the time the detector went off, the entire motorhome would be about 85% full of carbon monoxide and my wife and I, plus anyone else that might be visiting, would be dead before the alarm went off. I continue to be amazed at Fleetwoods commitment to quality.
Hope you get it fixed and the fix is simple.