Good effort Roger - you found it.
Have your 3 hydraulic slides' mechanisms ever been cleaned/lubed? Humidity may have an effect on that part of things; the issue likely isn't hydraulic. And Lee is right - humidity could be affecting the resistance of a main electrical connection at the pump, so all the slides react the same. Check for corrosion and tightness of all motor leads. Just driving from S.C. to Florida may have micro-changed a bad connector enough that it's temporarily making adequate contact again, but it'll falter once more sure as shootin', maybe not allowing slideout operation at all.
-Joel
(still not sure what fluid to use guys ... ?)