The stock cable on Sennheiser cables is pretty bad, it's really just two cables that are glued together, with a piece of heatshrink to keep them together so that the cables don't peel apart, but that heatshrink over time gets loose and starts moving down the cable and allowing it to separate more. I thought this was pretty annoying but didn't want to spend the money on a new cable, so I modeled this up in Fusion 360 pretty quickly so it behaves more like a better cable with a proper plastic junction.

I split the part in two halves in OrcaSlicer, then melted the edges together with my soldering iron, but I'm sure you can just glue it, or maybe you could print it in one piece with a pause in the middle to put the cable in, I didn't want to risk melting the cable with the nozzle however.