That's an odd form of separation, but I read through that thread and if it is in the middle of a group in a metal assembly, it kind of has to be cement failure. Probably rosin for the cement with that age, the UV cure is relatively new.
Take that assembly out and take more pictures of the inner end and if there are any details of the sides. A lot of the tail pieces have rings to hold 2 groups in place, odd to have a larger stackup like that all glued together.
Take that assembly out and take more pictures of the inner end and if there are any details of the sides. A lot of the tail pieces have rings to hold 2 groups in place, odd to have a larger stackup like that all glued together.