GX450 Serial Echo autonomously turning on

I have two customers that are using the GX450 modem with our product in the field. We are essentially using the GX450 as a serial to wireless terminal server. Our device configures the Modem using AT commands at boot and once it is initialized we send protocol information from our serial port to a remote location.

This works fine and we have used this exact implementation with multiple modems. However in the last three weeks we have seen a problem with two different customers at multiple locations. We have determined that the modem is suddenly turning local echo on to the Serial Port. Our device will absolutely NOT work with the local echo on so all of the modems are configured to have the Serial Local Echo off.

MY QUESTION: Why are GX450 modems deployed in the field suddenly having the Serial Port Local Echo activated? How can we stop this from happening?

Both customers have tried to turn this setting back to off in the field only to find that it is back on when the modem resets.

Some points:

  • these modems have been in the field working without issue prior to this issue appearing recently.
  • our device does not touch the Echo settings as part of the initialization routine.