You might want to take a look at https://bugs.launchpad.net/ubuntu/+source/modemmanager/+bug/686418
For the initial bug reporter, the corresponding line in file "/lib/udev/rules.d/77-mm-usb-device-blacklist.rules" would be
ATTRS{idVendor}=="03f0", ATTRS{idProduct}=="241d", ENV{ID_MM_DEVICE_IGNORE}="1"
to force modemmanager to ignore the initial /dev/ttyUSB0 for firmware loading.
You might want to take a look at /bugs.launchpad .net/ubuntu/ +source/ modemmanager/ +bug/686418
https:/
For the initial bug reporter, the corresponding line in file rules.d/ 77-mm-usb- device- blacklist. rules" would be
"/lib/udev/
ATTRS{idVendor} =="03f0" , ATTRS{idProduct }=="241d" , ENV{ID_ MM_DEVICE_ IGNORE} ="1"
to force modemmanager to ignore the initial /dev/ttyUSB0 for firmware loading.