Powerbeats wire expanding and leaking grease

I have a pair of Powerbeats purchased in 2018. Over the last year, the rubber that encases the wire has been expanding. It looks like it is filling up with air or some fluid. It recently expanded so much that the expanded portion reached the junction between the wire and the earpiece, then some kind of grease started leaking out of the junction. It continues to leak every day. The beats themselves are working fine, except for the microphone which stopped working about a year ago. What is this grease? Why did this happen? How can I stop the leaking? This doesn't seem like a common issue as I can't find any other information about it.