There are a plethora of outstanding issues. This forum is full of them.
A couple cases in point: The way the Modular screen always re-scrambles all the modules, organizationally, any time you go to a different screen and come back.
The sampler is barely functional, inasmuch as it can load and play samples, but that's about it. We can't even preview changes to an individual sample when adjusting start and end points. We can't adjust the trigger velocities for layering. We can't drag-n-drop into the Sampler itself, only onto the pads.
And then there's the way Spark2 insists on saving a new instrument every time you modify a kit, which ends up making the Instrument Library screen a serious pain in the ass to use, at best. Particularly with no search or rating functionality. The only way to remove all these extraneous instruments is to delete the projects from which they came. Ridiculous and largely useless workaround.
Throughout this forum are numerous other issues that really need to be addressed.