I also have z-wave and firecracker, each using a USB port on RPi. I had z-wave first and it worked fine. Then I plugged in firecracker and it worked fine as well. But, after the first power interruption, when the RPi came up, the port numbers changed and z-wave and firecracker did not work. I re-configured HG (Z-wave port, firecracker port) and all worked. After that, the ports stayed the same through power interruptions and both z-wave and firecracker work. So, after a power interruption, do not unplug any USB's, just configure HG to use the correct ports. If you plug/unplug USB's the OS may change the port numbers depending on where you have things plugged in. At least, that's my understanding. Good luck.