I'm porting a working app from SDK 1.1 to 1.2, and have noted that when I make an mqtt connection close it, and re-open (to a different mqtt server) that the call to nrf_connect hangs indefinitely.
The socket number is the same, which makes me think that when the first connection closes, it leaves something in a bad state.
The two separate mqtt connections work fine in isolation from each other, just not when the connections are made sequentially. (open, close, open)
Also, I've noted that when I modify the code to make both connections one after the other, forcing the use of another "new" socket for the second connection, things work fine.
This worked fine with modem firmware 1.1.1 and SDK 1.1, so it seems like it might be a new SDK 1.2 bug.