Quoted from bigguybbr:Iām not sure I buy into that. There is something with a grease like consistency packed into the socket that was oozing out.
It happens from time to time in early solid state games. The slime oozes mostly out of blue, green and black colored wires likely a reaction between the plastic insulator dye and the copper.
https://pinside.com/pinball/forum/topic/stern-ali-green-goop#post-5271645