if i had to take a wild stab at it... i would say the power coming from the 2 USB data wires are degrading too much to send info out to all 20 gridseeds.
the powered usb blocks will send extra power to the + and - on the usb devices however it does not pump up the voltage for the USB data connections and could be causing hardware errors and acting like everything is shorting out due to low voltage on the two data wires
you could try shorter usb cables. usb cables with thicker data wires, or just go buy another PI.
a second PI may be the cheapest idea.
if i was any help send me some BTC
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