Hard Drive Updates: Check for and update external hard drive firmware if available. For Intel based Macs, perform an SMC and PRAM/NVRAM reset SMC.: Perform an SMC reset: https://support.apple.com/en-us/HT201295   Perform an NVRAM/PRAM reset: https://support.apple.com/en-us/HT204063  Disable Power Nap on Mac (in power settings, disable for when connected to AC power and battery if the customer uses the hub while also on battery power). If possible, test the USB hub and hard drives with a Windows PC to see if the issue persists there as well. If this issue persists, if possible we have a tool that automates collecting a set of log files from your system. You can download the PlugDebug tool and learn how to use it by clicking on this link:plugable.com/plugdebugEnsure that you have the USB Hub connected to the computer when the PlugDebug application is run. Then send us a copy of the log files to Support@Plugable.com