When using adb -s to run commands on Firefox OS devices; e.g. for flashing/pushing files etc, some of our test devices (Inari) use the serial number used as the device identifier.
E.g something like this: 11:22:33:44:55:66
This is a problem as the colons cause mis-interpretation of the device identifier.
A workaround is to run adb devices -l and use the usb:<whatever> string (a.k.a the device qualifier) in place of the device identifier.