There are no known bugs in regards to SMS utilities.
The logs you have provided also do not indicate any messages received by the router.
Did the router not respond to reboot, status, and sim_switch commands only, or all SMS commands at all?
It would be interesting to know if you are able to send SMS messages from both, 7.2.7 and 7.3 firmwares. A helpful hint might be if you could SSH to the router before sending/receiving SMS, run command logread -f and then attempt to send/receive SMS to check what, logs does the device generate during these events.