Water soluble salt in distillate?

Hi all!

I hope you could give me some answers. So I have a binary liquid mixture. in the water phase i have a water soluble salt. First I pass it through a film evaporator, than simple distill it. All of that in medium vacuum. How it could be possible that the water soluable salt is still in the destillate? Not all but still a significant amount.

Thank you for any kind of answers!