I had the same problem today. I pulled the ear bud apart further to see if there was any exposed wires or other metal parts touching. I’m not sure if just moving it around caused the squealing to stop, but I then held it tightly together to see if in the position everything was in would cause the squealing. Once I verified that it would not I filled the cracks in with super glue and let it dry (10-15 sec). Seems to be working normally now.