sierra modem recognized on wrong port

[Jordan Moncharmont <jmoncharmont teslamotors com>]

Hey,

I have an issue similar to http://www.mail-archive.com/networkmanager-list gnome org/msg14551.html

I'm trying to connect a sierra device and occasionally it incorrectly connects on ttyUSB3 instead of ttyUSB4.

Here is the lsusb output:
http://pastebin.com/iwuUKG6u

The modem talks on ttyUSB3 and ttyUSB4, here's the pwds of each device:
/sys/devices/pci0000:00/0000:00:1d.7/usb2/2-6/2-6:1.3/ttyUSB3/tty/ttyUSB3
/sys/devices/pci0000:00/0000:00:1d.7/usb2/2-6/2-6:1.4/ttyUSB4/tty/ttyUSB4

Can you help me get some new rules to ensure that this device connects on the right port?

Thanks,
Jordan