This hylotelephium should be well completely dry with no leaves in winter. I guess you must be leaving in a very hot or at least hot climate that this did not happen, because otherwise it is normal for all leaves to fall off and then for the stem and flowers to skeletonize.
Other than that, problems with leaves in my experience happen when there is something wrong with the roots, either the roots entangled completely because of being grown in a small pot initially, like "plugs" and they strangle themselves and cannot get nutrients or either the roots are rotting.
But I have not grown these plants in such a climate where they do not dry up for the winter with leaves falling off, so I am not quite sure why they aren't skeletons with small buds at the based of the stems at the soil level.
