Created simple demonstartion as follows:
Started with brand new device, completed config wizard, setup mobile connection as QMI to EE (note recent firmwares display it as 'EE EE' on all models), created SMS group with single number, configured SMS status command as No Authorisation, from group just created. Send Status sms to device and received response after a few seconds.
Changed mobile connection to PPP, and checked device had reconnected. Sent status sms to device but received no response. After a couple of minutes checked SMS list and message had been received.
Changed mobile connection back to QMI, checked device had reconnected. Sent status sms and status response received as expected.
Dumped troubleshooting file(attached).
Log shows processing of SMSs in QMI mode but no corresponding entries when in PPP mode.
Also of note is that there is a further issue even when using QMI mode (possibly associated) when VPNON and VPNOFF sms messages are sent to this model the relevent OVPN config is set as enabled/disabled as expected but connection/disconnection is not actually actioned (until reboot). With same firmware version on RUT950U002xx the VPN connection is connected or disconnected as requested, although those units are using PPP mode for mobile connection, I have not yet tested it in QMI mode as I currently don't have access to a local RUT950U002xx and can't jeopardise a remote one in the field.
Troubleshooting File