Our Norcold refrig model N821 (in 2010 Arctic Fox TT) is freezing food on the top shelves at the lowest (warmest) setting (1). Can't set it any warmer. Don't know what to do. Manual no help. Have been running on electric. Tried LP, no difference. We are in eastern PA with high humidity (75%) almost all the time and frequent high temps (80-90's) until this week - lower temps, same humidity. Any suggestions?