I have a few MC7455 modems connected using the qmi_wwan driver (on linux 4.14.171) managed by modemmanager. After some time a few of these modems have completely stopped responding to any commands over QMI, not showing up in modemmanager. The AT command serial port (/dev/ttyUSB2) and the NMEA serial port (/dev/ttyUSB1) are both missing. The only port that is available is /dev/ttyUSB0, which seems to be for diagnostic monitoring. Nothing is sent over this port, however.
This issue persists after a cold reboot. The qmi_wwan driver doesn’t show anything strange in dmesg log. What could be causing this issue? Thanks in advance.