Tom, I have seen this and the cane dies, the rest of the plant is not affected, don't know what it is. There is a condition in gooseberries known as dieback, it is caused by a greymould fungus I think. Since Crandalls are more closely related to gooseberries, that may be the problem. I cut the cane off as close to the ground or main stem as possible as soon as I notice it.
Ed
Northumberland BerryWorks
707 Front Street
Northumberland, PA 17857
(570) 473-9910