@cronjoblover
I know "only" a work around that I will using in the next month by my self because my modem is also usb connected and looses here and there also the connection.
It looks then like this entry here:
Enter an option: ugen0.2: <Sierra Wireless, Incorporated MC7710> at usbus0 (disconnected)
u3g0: at uhub2, port 3, addr 1 (disconnected)
u3g0: detached
ugen0.2: <Sierra Wireless, Incorporated MC7710> at usbus0
u3g0 on uhub2
u3g0: <Sierra Wireless, Incorporated MC7710, class 0/0, rev 2.00/0.06, addr 1> on usbus0
u3g0: Found 6 ports.
And my modem is normally on ugen0.3 and so it comes that I even again and again must go back to the config
and set the new "ugen" up!
I will go with a small RapsBerry Pi 3/4 with daughter board
on top with SIM and that miniPCIe modem and a mSATA
at the bottom site. Then I can connect it to the pfSense
over ethernet! I hope then getting less disconnections.