Same thing here. Since the latest Rig Manager with the new USB-Driver (I'm on a Mac with the latest High Sierra) I got the same experience from time to time when connected to the computer. To make this clear: This happens when the Rig Manager is not running at all! There were known problems before when the Rig Manager was connected but the computer went into hibernation. But now this happens even when the Rig Manager isn't even running. This is bad at home but terrible one stage if connected to a computer.
Same in my case, I was suspecting about Rig manager and Usb connetction (when my Mac sleeps ), nice to know about IT because os a minor problem for how i use my kemper