Image on left is from 4 days ago, but the pimple was slowly forming over around 2 weeks.
The goop was sticky, not oily. Earphones are Panasonic RP-TCM130.
I was not able to find an explanation.
Something to increase cable lifespan, lubrication, rubber disintegrating, sweat and earwax that somehow got into the cable, dielectric grease, no clear answer.
At first I thought the wires just somehow twisted. Nope.
I am so intruiged by the fact that the mass of good accumulated at the one spot. The mystery of what pressures were at play for it to flow to that one spot.