I have an Aerangis biloba which has been growing well all summer and developed two growing points and about 6 leaves on each. Within 2 weeks half of the leaves dropped off the plant. The leaves were still green and fresh when they dropped and the plant has nicely growing roots (and plenty of them). The same happened to another Aerangis biloba last winter: it eventually lost all leaves and died.
None of my other Aerangis are affected. I am wondering whether this is a disease or some cultural problem.
I had the same problem with one of my Aerangis (Aerangis luteo alba var. rhodosticta) last winter. It lost almost all leaves, some 2-3 left. Now its back, has some new growing points.
What I found was, that some times I had some water left in growing center and this particular plant is tied to bark very upwards.