No the problem hasn’t been solved. Certain USB hard drives will not be mounted properly under the v4.x firmware. In my case, which I discussed in this thread, I had to repartition and reformat a Toshiba external USB 3.0 hard drive in a Windows PC before the My Cloud v4.x firmware would properly mount the drive. The default facotry formatting of the drive by Toshiba seems to have been the culprit under v4.x firmware, even though it mounted properly under the v3.x firmware.
One thing to try, connect each drive one at a time to the My Cloud. Use the eject option within the My Cloud Dashboard to eject the USB drive when finished with it. It is possible there may be a limit to how many drives can be mounted or supported at one time by the My Cloud.
