Can you try putting a non usb powered hub between your powered hub and your RPI.
Yes..in my rig I have a power USB hub with USB adapters (HIGHROCK 30cm USB 2.0 a Power Enhancer Y 1 Female to 2 Male Data Charge Cable Extension Cord(1pc) that connect the USB port of my CPU. So, the MLDs draw power and communicate as so. The cost of the adapters was annoying (~$5 USD ea.) but it works.