That picture is so large I can't see it all at once, but "yellow buildup" on a fridge says, to me, that you had a leak in the lines (ammonia) and need a new mechanism or a new fridge.
I'm sure others will be along with more info, but you could help them by cutting the pixel size of you pic to, say 900x600 or such, and by telling what fridge (brand and model) you have. While it probably wouldn't make much difference in this case, putting your RV type/model in your signature can be very helpful in getting help on many problems.