So I'm having a problem with my 2015 MacBook Pro 15". I've had the logic board replaced before for issues relating to Kernel Panics upon wake, but this is a new one. I've been having problems with USB devices randomly disconnecting and reconnecting for no reason. It does not do this to mass storage devices (USB sticks, USB hard drives, etc) but it does it to USB electronics (iPhone, Garmin GPS, etc). For instance, I went to restore my iPhone via DFU mode tonight and was greeted with an Unknown Error 9 when it tried loading the firmware to my iPhone. I tried both ports, different USB cables, reinstalling iTunes, rebooting both devices, on and on, to no avail. I was finally to try it with another machine, and it worked the first time, no errors. Earlier this evening I tried sending data to my GPS for an upcoming trip, and the Garmin software kept reporting a communication error with the device. The GPS, which shows as a removable disk in the Finder, would also randomly disconnect and reconnect to the computer. When I got my hands on the other machine, I tried it as well, and had zero issues. So my question is, does this sound like a problem with the USB drivers in macOS, or a hardware level issue with the USB bus (power or data related)? I'm going to try an E&R on the boot drive, see if that makes a difference, but I wanted community input before I do. TIA!