I had a similar occurrence with the propane detector in my TT. The mentions of low voltage were dead on but turns out it also wasn't my batteries. I found that the wiring connection right at the propane detector only had a few wire stands connected on one of the connections. Those few strands did not have the capability to transport enough amps to the detector at times, hence the propane detector would periodically go off.
Before spending the money on a new one, I'd take a quick look at the connections on the back of your existing detector first.