Summary

Replacement for Sony 1000XM5 Coupling

For best results, use a soldering iron to melt and fuse the coupling to the headphone swivel.

Some disassembly may be required for easier access (Earmuff, 8 Screws, headphone back cover, ribbon cable, wire retaining plate/ screw)

Cut or trim the existing broken coupling at the base of the swivel and sand it down smooth. Then, melt and fuse the Coupling Outside perpendicular to the Swivel base. Be sure to add excess filament material to strengthen the bond. When externally and internally secure, pinch together tightly the couplings around the headband Swivel and solder the edges, and release the pinch when bonds have cooled and secured.

Optionally, after parts have been bonded, make 2-4 vertical incisions around the swivel coupling against the bond 1-2mm deep and melt filament into the voids.
I used PLA filament to print these parts and filled the voids with soldered Nylon (Zip ties).