if thats where you run it at 40 i suspect it's overheating and shut off possibly broken now , one should never set a humidistat less than say 66%rh as a normal house is 70%rh and asking anything more of a home unit is just not possible if moisture is that much a problem try running two units about twenty feet apart , they will cycle more to cool down and will run longer , might even be more efficient than running one harder
