MC8705 locking up

I have a client who is using a KonTron sbc running OpenSuse 12.2 linux and sierra drivers to control, and send data to, a MC8705 using ppp.
Every 2 days(approx) the module appears to lock and not send data.
I have determined that the application is still running during lockup.
The software uses ttyUSB3 for control and ttyUSB4 for data.
I have tried to use extended AT commands to force a watchdog reset if connection fails but found another issue.
The sierra drivers lock ttyUSB3 so I cannot send AT commands to the module while the app is running.
I disabled the application startup so that I could communicate using minicom but most of the extended AT commands return ERROR.
Any Ideas what may be wrong?

which driver version are you using?

Most of the extended AT commands are password protected. So to use these commands, you must enter the correct password using AT!ENTERCND.