Hi,
Slicer is "sensitive" to the geometry - both the slicing and being-sliced.
It gets even more sensitive when there are many objects being cut which lay over each other from a specific view.
So make absolutely sure there is no bad geometry. The good practice with slicer is to have capped, bound volumes of slicer and sliced objects.
Planar slicer is not supported (I have tried very hard to push this idea) and slicer cannot exclude itself - you cannot have objects with multiple elements, one of which is a slicer, it will cut itself, and you will need to separate the slicer into a different object.