Sprint updates are soft-bricking nodes #54
Description
Sprint updates are causing nodes to stop reporting in the field. When Sprint initiates an update, the updater starts writing strings of the form '#9XX' to the cell module's RX buffer. This is causing the parser to fail, and thus the node can't communicate with the server (modem_send_recv returns 0).
In general, AT commands shouldn't be issued during the update process, as it can cause activation/updates to fail. The proper way to deal with this problem should be to put the module in standby when '#900' is detected and then not send any AT commands until another '#900' is detected. We can also tell Sprint to not send updates to these cell modules.