AT+CIPSHUT return ERROR

[JoeCheng]

I am working a project for TCP/IP using SIM7000 NB-IoT module.

The TCP/IP process is OK at the beginning.
After several hours if signal quality is so bad that connection is failed like,
———————————
15:42:38.101 ,AT+CIPSTATUS
15:42:38.101 ,OK
15:42:38.101 ,STATE: IP STATUS
15:42:38.163 ,AT+CIPSTART=”TCP”,”xxx.xxx.xxx”,”80″ // “xxx.xxx.xxx” is our server host name
15:42:38.163 ,OK
15:43:28.079 ,+PDP: DEACT
15:43:30.225 ,STATE: IP STATUS
15:43:30.225 ,CONNECT FAIL
15:43:30.287 ,AT+CIPSTATUS
15:43:30.287 ,OK
15:43:30.287 ,STATE: IP STATUS
15:43:55.225 ,AT
15:43:55.225 ,OK
15:43:55.225 ,AT+CPIN?
15:43:55.240 ,+CPIN: READY
15:43:55.240 ,OK
15:43:55.256 ,AT+CGDCONT=1,”IP”,”nbiot”
15:43:55.256 ,OK
15:43:55.521 ,AT+CNMP=38
15:43:55.521 ,OK
15:43:55.834 ,AT+CMNB=2
15:43:55.834 ,OK
15:43:55.834 ,AT+CSQ
15:43:55.850 ,+CSQ: 99,99
15:43:55.850 ,OK
15:43:55.896 ,AT+CIPSTATUS
15:43:55.896 ,OK
15:43:55.912 ,STATE: IP STATUS
15:44:20.789 ,AT
15:44:20.789 ,OK
15:44:20.805 ,AT+CPIN?
15:44:20.805 ,+CPIN: READY
15:44:20.805 ,OK
15:44:20.805 ,AT+CGDCONT=1,”IP”,”nbiot”
15:44:20.820 ,OK
15:44:21.132 ,AT+CNMP=38
15:44:21.132 ,OK
15:44:21.429 ,AT+CMNB=2
15:44:21.444 ,OK
15:44:21.444 ,AT+CSQ
15:44:21.444 ,+CSQ: 99,99
15:44:21.444 ,OK
15:44:21.507 ,AT+CIPSTATUS
15:44:21.507 ,OK
15:44:21.507 ,STATE: IP STATUS
15:44:46.393 ,AT
15:44:46.393 ,OK
15:44:46.393 ,AT+CPIN?
15:44:46.409 ,+CPIN: READY
15:44:46.409 ,OK
15:44:46.409 ,AT+CGDCONT=1,”IP”,”nbiot”
15:44:46.424 ,OK
15:44:46.741 ,AT+CNMP=38
15:44:46.744 ,OK
15:44:47.047 ,AT+CMNB=2
15:44:47.049 ,OK
15:44:47.056 ,AT+CSQ
15:44:47.058 ,+CSQ: 99,99
15:44:47.060 ,OK
15:44:47.118 ,AT+CIPSTATUS
15:44:47.120 ,OK
15:44:47.125 ,STATE: IP STATUS
15:45:12.001 ,AT+CIPSTATUS
15:45:12.001 ,OK
15:45:12.001 ,STATE: IP STATUS
15:45:12.064 ,AT+CIPSHUT //”AT+CIPSHUT” return ERROR, the state can’t change from “IP STATUS” to “IP INITIAL” ???
15:45:12.064 ,ERROR
15:45:12.079 ,AT+CIPSTATUS
15:45:12.079 ,OK
15:45:12.079 ,STATE: IP STATUS
15:46:37.236 ,AT
15:46:37.236 ,OK
15:46:37.236 ,AT+CPIN?
15:46:37.236 ,+CPIN: READY
15:46:37.236 ,OK
15:46:37.251 ,AT+CGDCONT=1,”IP”,”nbiot”
15:46:37.267 ,OK
15:46:37.579 ,AT+CNMP=38
15:46:37.579 ,OK
15:46:37.882 ,AT+CMNB=2
15:46:37.882 ,OK
15:46:37.897 ,AT+CSQ
15:46:37.897 ,+CSQ: 99,99
15:46:37.897 ,OK
15:46:38.100 ,AT+CIPSTATUS
15:46:38.100 ,OK
15:46:38.100 ,STATE: IP STATUS
15:48:17.638 ,AT
15:48:17.638 ,OK
15:48:17.653 ,AT+CPIN?
15:48:17.669 ,+CPIN: READY
15:48:17.669 ,OK
15:48:17.669 ,AT+CGDCONT=1,”IP”,”nbiot”
15:48:17.700 ,OK
15:48:17.982 ,AT+CNMP=38
15:48:17.982 ,OK
15:48:18.294 ,AT+CMNB=2
15:48:18.294 ,OK
15:48:18.294 ,AT+CSQ
15:48:18.294 ,+CSQ: 99,99
15:48:18.294 ,OK
15:48:18.510 ,AT+CIPSTATUS
15:48:18.510 ,OK
15:48:18.510 ,STATE: IP STATUS
15:49:58.024 ,AT
15:49:58.024 ,OK
15:49:58.040 ,AT+CPIN?
15:49:58.040 ,+CPIN: READY
15:49:58.055 ,OK
15:49:58.055 ,AT+CGDCONT=1,”IP”,”nbiot”
15:49:58.071 ,OK
15:49:58.367 ,AT+CNMP=38
15:49:58.367 ,OK
15:49:58.681 ,AT+CMNB=2
15:49:58.681 ,OK
15:49:58.681 ,AT+CSQ
15:49:58.681 ,+CSQ: 23,99 //Signal Quality is OK!!
15:49:58.697 ,OK
15:49:58.697 ,AT+CIPSTATUS
15:49:58.697 ,OK
15:49:58.713 ,STATE: IP STATUS
15:49:58.759 ,AT+COPS?
15:49:58.759 ,+COPS: 0,0,”466 01″,9
15:49:58.759 ,OK
15:49:58.775 ,AT+CPSI?
15:49:58.775 ,+CPSI: LTE NB-IOT,Online,466-01,0xC442,56356995,62,EUTRAN-BAND28,9370,0,0,-9,-79,-69,16
15:49:58.775 ,OK
15:49:58.791 ,AT+CGATT?
15:49:58.791 ,+CGATT: 1
15:49:58.806 ,OK
15:49:58.806 ,AT+CGREG?
15:49:58.806 ,+CGREG: 0,1
15:49:58.806 ,OK
15:49:58.806 ,AT+CGNAPN
15:49:58.806 ,+CGNAPN: 1,”nbiot”
15:49:58.822 ,OK
15:49:58.822 ,AT+CIPSHUT //”AT+CIPSHUT” return ERROR, the state can’t change from “IP STATUS” to “IP INITIAL” ???
15:49:58.822 ,ERROR
15:49:59.807 ,AT+CSTT=”nbiot”
15:49:59.807 ,ERROR
15:50:00.353 ,AT+CIPSTATUS
15:50:00.353 ,OK
15:50:00.353 ,STATE: IP STATUS
———————————-

The retry process will be NG at “AT+CIPSHUT” always.
//”AT+CIPSHUT” return ERROR, the state can’t change from “IP STATUS” to “IP INITIAL” ???

Recovery Try:
AT+FUN=0
AT+FUN=1
Result : the same NG condition.

Reset the SIM7000 module will fix this issue.
Is there any AT Command to change the the state from “IP STATUS” to “IP INITIAL” forcibly??
or Is there any AT Command to reset the SIM7000 module ?

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