Hi,
as discussed in different issue on DevZone. We have discovered that send command freezes the program in the CoAP client sample. The Nordic employee Hakon has confirmed that it also happens on his board.
Could you please try to inspect the issue? Unfortunately, we are not able to collect the modem trace right now our DK broke up and we are not able to collect traces on our custom board.
The modified sample could be downloaded under this link: devzone.nordicsemi.com/.../coap_5F00_client.zip