I read thru the manuals after picking up Ollie, and the Dometic Refrigerator User Manual says: "Use the Airing Position Card to keep the doors ajar if the refrigerator will not be in use for an extended period of time or put in storage." I figured they supplied this Airing Position Card, but no, it is an accessory. I found one on eBay for $6. More expensive than an old sponge or a rag, but it works well. When we start our trip, I toss the card onto one of the fridge door shelves, and I can easily find it at the end of the trip.
I did a google search today for "dometic 3312986403 rv refrigerator door airing position card" and eBay prices seemed to be $17. No CamelCamelCamel for eBay. Today Dyer RV Parts has it for $11.99.