Lyman's hand gun "Accumeasure" (the Lil' Dandy was RCBS), like any powder volume measurement tool, cannot possibly drop coarse materials as well as finer materials. Unique is a coarse flake powder, ball powders are fine enough to flow like water through about any measure.
Powder contains some small quanity of volitale solvents. A given volume of new powder will always be slightly heavier than the same powder after some time because of the loss of solvent. Therefore, not obtaining a consistant weight even for a precise volume is not a shortcoming of any measure, it's just a fact of life.
As RC correctly observes, the slight variation you are getting with your Unique charges is meaningless. Weighing handgun charges to a tenth is a slow exercise in futility. Drop 'em and shoot 'em.