Error 50 | Telit Cinterion IoT Developer Community

We are using a GSM Modem Conterion EHS6 Terminal USB together with the alerting system PageControl. Normaly this works fine.
Now we have  a client in Belgium, there we get the message  from the modem: error 50

I have found following entry in this forum:
https://iot-developer.thalesgroup.com/threads/cme-error-50-when-entering...
=> '+CME ERROR: 50' means Incorrect parameters

But how I can find out which parameter is not correct?
We use the same parameters like on other plants.

I have a log, but with my knowlegde I cant find out which parameter is wrong. Perhaps somebody can give me a hint?

<TRACEDATE:13.12.2019>
14:53:14.921 ModemConnectSer(14, 115200, 8N1)
14:53:14.921 ModemResultReset
14:53:14.921 ModemResultReset
14:53:14.921 ModemFlushCommand
14:53:14.921 ModemResultReset
14:53:14.921 ModemSend: ATH
14:53:14.921 ModemSend: {0D}
14:53:15.031 ModemResult: OK (=00000100)
14:53:15.031 ModemSendCommandDone
14:53:15.031 ModemResultReset
14:53:15.031 ModemSetUserPrompt(1): +CSQ:
14:53:15.031 ModemResultReset
14:53:15.031 ModemSetUserPrompt(2):
14:53:15.031 ModemResultReset
14:53:15.031 ModemSetUserPrompt(3): 
14:53:15.031 ModemResultReset
14:53:15.031 ModemSetUserPrompt(4): 
14:53:15.031 ModemResultReset
14:53:15.031 ModemSetUserPrompt(5):
14:53:15.031 ModemResultReset
14:53:15.031 ModemSetUserPrompt(6):
14:53:15.031 ModemResultReset
14:53:15.031 ModemSend: AT+CSQ{0D}
14:53:15.140 ModemResult: +CSQ: (=00010000)
14:53:15.140 ModemResponse:  5,99
14:53:15.140 ModemResult: OK (=00000100)
14:53:15.140 ModemResultReset
14:53:15.140 ModemSetUserPrompt(1): >
14:53:15.140 ModemResultReset
14:53:15.140 ModemSetUserPrompt(2): +CMGS:
14:53:15.140 ModemResultReset
14:53:15.140 ModemSetUserPrompt(3):
14:53:15.140 ModemResultReset
14:53:15.140 ModemSetUserPrompt(4):
14:53:15.140 ModemResultReset
14:53:15.140 ModemSend: AT+CMGS="
14:53:15.140 ModemSend: +49159******
14:53:15.140 ModemSend: "
14:53:15.140 ModemSend: {0D}
14:53:15.140  (=00040000)
14:53:15.140 ModemResultReset
14:53:15.249  (=00040000)
14:53:15.249 ModemResultReset
14:53:15.249 ModemResult: > (=00010000)
14:53:15.249 ModemSetUserPrompt(1):
14:53:15.249 ModemResultReset
14:53:15.249 ModemSend: 13.12.2019 13:49:15 MSG02 PLC01 System FaultModemSend: {
14:53:15.249 1A}
14:53:15.249 ModemResult: (=00030000)
14:53:15.265 ModemResultReset
14:53:16.681  (=00040000)
14:53:16.681 ModemResultReset
14:53:16.691 ModemResult: ERROR (=00000500)
14:53:16.709 ModemResponse: : 50
14:53:16.709 ModemResultReset
14:53:16.725 ModemResultReset
14:53:16.743 ModemDisconnectSer(14)
14:53:17.091 ModemConnectSer(14, 115200, 8N1)
14:53:17.091 ModemResultReset
14:53:17.110 ModemResultReset
14:53:17.110 ModemFlushCommand
14:53:17.126 ModemResultReset
.....

Allready best thanks?
Daniel