Have no idea other than a guess. Sounds like it is measuring the temperature from the return somewhere rather than room temperature. So temperature is "SATISIFIED" and shuts off. A short time later the fan starts to "measure" the temperature and it still satisfied so the compressor does not start and fan shuts off. I have an atwood 15,000 BTU that does same on heat pump. Love it on acnd but heat pump drives me crazy and will not get the room temperature up satisfactorily. Per atwood that's the way it was designed to work.