What would cause a WD My Book external drive to have issues with mounting in Mojave? It's not a formatting issue that I'm aware of since I've added data just fine but the symptoms are: I can read/write to the external drives with everything working as it should be but the next day when I go to mount the drives, nothing works UNLESS I unplug and replug the USB. Then, everything is fine for a period of time. If this were happening to one drive, maybe I'd try re-formatting it. However, this happens on other external drives as well. The computer is an iMac w/Retina. Thanks for any suggestions or observations.