There is a odor coming from the stove and ventless wall unit when in use.?

We use liquid propane for heating and cooking. There is a odor coming from the stove and ventless wall unit when in use. We had our gas supplier inspect the system no leaks and good pressure. He doesn't know what is is other than it reminds him of the smell from kerosene. Have you any knowledge of this? We also have the same wall unit in our well housethere is no odor coming from it. All our gas comes from the same tank. The unit have been cleaned for the season