MKR NB 1500 freeze with Arduino IoT Cloud

Hi guys,

I have tried to use the MKR NB 1500 board with Arduino Cloud and I am stuck with a major instability issue.
Network coverage is 31/31 and the board is sitting at my desk all the time.

At about 30% of all attempts to set up the connection (starting the from the ArduinoIoTCloud template), the device hangs and fails to open the socket the mqtt server. The whole sketch will also freeze because of this!
I found that the modem hangs when the driver issues the AT command

**AT+USOCO=0,"mqtts-sa.iot.arduino.cc",8883 **

...which should open the socket. Unfortunately it sometimes locks the AT interface...

The thing is that if i change this server adress to another server, it does not hang!!

My setup
MKR NB 1500 without shields
SARA FW revision=L0.0.00.00.05.06 Feb 03 2018 A.02.00

Libraries:
ArduinoIoTCloud Ver 0.11.2
MKRNB 1.3.2

What can I do? Is this normal behaviour?