My '14 621 would not hold ice very well so I opened up area to see under deck and there was no insulation except for slight flotation foam in a small spot under it. I don't understand why. It should be.
Anyway I did it myself with spray foam. Not sure if it will suck water but don't think it could too much.
Tested today and the thing is like a Yeti now. Maybe better. Check the insulation yours ain't working to good.
No time to let a dealer do it.