Some of the B C lampholders are designed not to be taken apart. You only find out after wrecking one.
There is a ratchet mechanism that allows it to be screwed together, but not unscrewed. If you can insert a thin screwdriver (Unplugged from the mains, obviously) the two metal "pawls" can be bent away from the teeth moulded into the composite outside, and then it can be disassembled to repair or replace the wiring.
Howard