If a succulent drops leaves on only one side, it is most likely black rot.
Q: Why do the leaves drop on one side while the other side is fine? A: You will know why once you behead it. As soon as this condition is noticed, it should be beheaded promptly, cutting until the stem is clean; the cut-off part can be left to dry until the wound heals, and then it can be propagated as a cutting. ...

Q: Why do the leaves drop on one side while the other side is fine?
A: You will know why once you behead it.
As soon as this condition is noticed, it should be beheaded promptly, cutting until the stem is clean; the cut-off part can be left to dry until the wound heals, and then it can be propagated as a cutting.