If memory serves, and it does not very well anymore
, I used HS-6 years and years ago for some kind of reloading. As I remember it I never got anymore because it did not meter very well through my Uniflow. The most consistent powders I have ever used in my Uniflow are all ball powders. I have since got a Chargemaster and oh what a difference it makes.
I think there could be something to what you think is causing the scale issue. I don't know how cold it gets in your garage but I do know electronic scales can be affected by extreme cold. You may want to contact Hornady and see what they have to say about it.