Yes, what O-B said. Our cooling fins drip tray has a drain hose that has a small orifice at it's end...no drip cup. This orifice, or in some cases, a duckbill flapper can get clogged with food debris or algae. Condensation can backup and overflow the fin tray.
Our pervious coach had the drain hose cup. A thin layer of vegetable oil helped hold cup water vaporizing to a minimum, stopping warm air from going up the hose causing excessive frost on the fins. We could then go the whole season without defrosting.