Are you saying that after you remove all the solids from the freeze-precipitated naphtha, and then blow on the resulting clear naphtha, it becomes cloudy? That would be kind of odd.
During any freeze precipitation, there is some spice still left in the naphtha. However, it should only have the maximum amount of spice soluble in freezer-temperature naphtha. When it returns to room temperature, or is gently heated (perhaps to 100-110 degrees fahrenheit), it becomes able to hold more spice. So if there is still spice in your plant material, you can let your naphtha return to room temperature (or gently warm it and the plant material up) and you'll keep pulling alkaloids. Then you put that in the freezer, and all of the extra spice precipitates back out as solids, but the naphtha again holds on to a certain amount of spice which is soluble even in very cold naphtha.
It's hard to tell how much spice is left in the naphtha -- depends on the temperature of your freezer, the brand of the solvent, etc. The only way to get all of the spice out of the naphtha is to completely evaporate the naphtha away. Given that you didn't just evaporate in the first place, I assume you're more concerned with purity than with amount of spice yielded where those two goals conflict.
With that note in mind, it's possible to get pure spice from evaporated naphtha if you dissolve the impure spice in acetone and add FASA to salt it out of solution. I won't provide all the details here because the information is on the forum and wiki, but basically you dissolve the impure spice in acetone, and in a separate container, you dissolve fumaric acid in acetone. Then you mix the two solutions together, and pure spice (as the fumarate salt, not the freebase) precipitates out as a solid. Decant off the acetone (which should contain the undesirable contaminants) and you ought to have rather pure spice fumarate. But that requires time and money to acquire another solvent and another reagent.