Seems like your AUC3 is broke. Alternatively it could be the dodgy usb ports on the pi. Try attaching a decent USB hub to run it off instead.
I agree it does seem that way. I tried a couple of different AUC3's but same result.
I'd like to try your suggestion with the USB hub. Would you set it up this way?:
Avalon controller (pi 3) -> USB hub -> AUC3 converter -> miner
Yes that's the only way you can plug it in anyway.