I recently replaced the earpiece speaker in a friend's iPhone 4. It's working, but it's very, very quiet. If the...

Well, crap. I switched from my trusty old 15” mid-2012 Macbook Pro to a 15” mid 2015 Pro. I ran into this same infuriating issue with my iPhone XS. I actually have two 15” 2015 Macbook Pros on hand at the moment, and it’s doing it on both. Running the sudo killall -STOP -c usbd command fixes it, until I reboot or wake the computer as others mentioned. Plugging in my 6S Plus is better, it usually works, but still does it occasionally on one of them. You can bet Apple will hear from me… Update (12/17/2019): Mine is working now. Apple serviced my mid-2015 15” MacBook Pro, replacing the motherboard and I/O board. (so they said, it still has the same serial number) I did notice one thing before I sent it in. As long as it was running macOS Catalina, I had no issues. Downgrading it to Mojave brought on the issues. Upgrading back to Catalina made it go away. However, it was not strictly software specific. The Genius Bar tech replicated it with ease using a triage drive in store. Once I got the laptop back, I...