That's odd. Was this the title bar of the connections page?
Pls see the atatched screen shot
Thanks Toralf! Pushed a fix for that, as well as a change so nyx can quit more quickly. However, unfortunately it won't help with the quitting issue you mentioned off list. That stacktrace indicated we got stuck terminating the controller itself.
Per chance were you logging at the DEBUG runlevel at that time? On a busy relay the amount of messages that slams the control port with can make it slow to shut down. Unfortunately besides that I'm at a loss for why it gets stuck for you. Looking at your debug logs would be the next step. Happy to discuss it off list if that would be ok.