@stephenw10 ok thank you I will try

You're workaround also fixed the issue for me! The issue on my machine was not because of manual disconnects; it was when probably renewing DHCP every 24h. Sometimes it would not come back online and it would give: « CHAT: The modem is not responding to "AT" at ModemCmd: label. » Error in log. power_off and power_on solved it without having to reboot the whole machine. Seems like for some reason /dev/cuaU0.2 was locked also but it doesn't appear in the logs.