mmhh - in V1.2 the command AT+CCHOPEN does not even exist anymore. beelogger says, that this could be the reason for the timeout as my chipset does not even respond to the command.
So somehow this Chipset SIM7600E-H deviates in a way that hinders communication and even if I find out what exactly it is, the beelogger guys would have to adjust a lot of things on their side only for me.
They have numerous systems running with an SIM7600E-L1C, so I have decided to abandon the attempt to integrate the SIM600E-H and get an L1C.
Does anyone need two SIM7600E-H? They are now for sale...
Thanks again for your support which eventually helped a lot to come to this conclusion.