This happened all the time in my former coach, a 2004 Newmar Kountrystar. It even occurred on my first trip in the coach which scared me to death.
It mostly happened on hot days. And of course no technician could ever figure out what the problem was.
Eventually it turned out that one of the hydraulic lines to the jacks was run close to a hot part under the coach. When the hydraulic fluid heated up it caused just enough expansion to cause one of the jack cylinders to descend about 1/4 inch, just enough to trip the alarm. Apparently it was a design flaw.
