Can't really call this a bug but as a behaviour it is certainly not ideal. VXLSE seems to divide the voxel into a fixed number of scroll points for those sliders, so if you are trying to maintain your cursor in the drawing position on any axis larger than say 80, you will jump by 2 instead of 1. On really large voxels it skips more like 2-3 layers.

On a related note, it might be handy to replace the sliders with text field boxes that actually tell you the numerical layer (if nothing else you know you where you are), with the bonus that the taller/narrower control would allow them side by side, AND make the arrow buttons larger. Those arrow buttons are nearly impossible to hit at high resolution, which forces you to scroll, which is inaccurate, compounding the issue.