1. First, follow the instructions given in this post by Bryan: https://www.spooky2.com/forums/viewtopic.php?p=95543#p95543 just to make sure the phantom ports are not the problem.
Then, if problem persists, disconnect all the generators from the USB hub. Disconnect also the USB hub, and connect generators one by one until problem starts again. This is to discard issues with the USB hub itself, and with the generators or cables associated.
2. I've been having the same problem with one GX after using the Phanotron. I solve it by turning off the generator, removing and reconnecting the USB cable, and then turning the generator back on.
For more details, please check the link from: