Mobile network is not working

[FOSSagent0]

Hi, i am so close to having a useable mobian-phone (UBPorts-Edition) and i am totally looking forward to. So thanks a lot for your work! :-)
What gives me a headache is getting mobile network to work.
My carrier is o2-germany and i can register for lte,umts and gsm and calls and sms are working so far.
But as soon as i connect to the internet the modem changes to state "unkown". I need to dis- and enable mobile in order to get the modem to register again.
I got the APN-Setup (apn: internet) of the carriers website. 

I tried phosh, modem-manager-gui and mmcli + nmcli. In pureos the modem fails exactly the same.
I am out of ideas for now so any help is appreciated.

I have a similar post on this subject, I have heard that it could be that the firmware on the cellular modem is corrupted. Have you contacted Pine64 about it? I think they should look into it in case it really is a case of faulty hardware.