Thank you so much for reaching out to us, I am sorry to hear that you are seeing this strange behavior, but I would be happy to clarify what is causing this issue.
Recently (in the release of Sierra) there has been an apparent issue with utilizing external HDDs/SSDs via USB hubs when connected to Macbook Pro, Macbook Air, and macOS based systems. We have reached out to Apple a number of times, and submitted multiple bug reports, but we have not received any information back. The problem does not specifically relate to just our products, and is effecting other hub manufacturers as well. The only two solutions provided are to directly connect the drive to your system, or see if adjusting the “spin down hard disks” option is not selected inside of System Preferences > Energy Saver.
There are multiple threads on Apple support forums from many different people running into the same solution, and if you would prefer, we would be more than happy to send various links on this forum post.
I hope this information helps, please let me know if you have any additional questions or concerns, and I would be more than happy to assist.
Thank you for your time,
Product Owner & Technical Support