Are you familiar with Blue Jade Vine diseases when they are planted outdoors?
The black in the branch runs all the way through, on bigger branches it looks triangular. The vines dry to a powdery wood "crumb" which disintegrates if you pinch it between your fingers.
Certified GKH Gardening Expert
I could not find specific diseases listed but I did find that this vine is very susceptible to root diseases if grown in soggy soil or poorly draining, heavy soil.
There is nothing that will help vines that have died off from this, but you could try amending the soil around the plant.