Szaky,
There is most definitely a problem with using the usb port to power devices from the controller. When the 3.0 controller came out I was hesitant to move to it because it was only wifi. Please note I am running 20 OS units. Mix of 2.2-3.0 units all spread out over 69 acres connected to ubiquity equipment that require lan. In any event, in working with Ray, he suggested a mini ap to get interface with it and to power it from the controller. Well I was seeing random failures that were difficult to trouble shoot. It ended up being multiple problems, one the controller would reset while pulling the logs due to a memory issue and the uptime api being added to the FW. While trouble shooting, I moved the mini AP router on to its own power source thinking that it was pulling to much power from the controller. This did not resolve the OS problem, but it did resolve the random problem with the mini AP resetting. After the firmware update which resolved the OS reset problem, I put the ap back on to the controller power and the AP random reset came back, but the controller did not seem to be resetting. So for some reason the OS usb port does a power cycle or something and causes weird behavior. So I do not recommend using it. I never further troubleshoot this any further, and I have not seen any other issues since.