In Affinity Designer 1.5.5 on Mac, when changing different parameters on the sliders one after the other, sometimes an unexpected parameter is changed. Sometimes, in a single drag, one then after parameter is changed. This seems to come from a certain behavior by design: if, short after dragging a slider handle you drag again by clicking on the area between two sliders, it will drag the last dragged handle. Except it does not only works for the areas just below or after the initial slider, but also others. The behavior was probably made to allow clicking not exactly on sliders, but causes bugs when playing with multiple sliders.
Animated gif to demonstrate. Problems occurs with RGB, CMYK, etc.