I am also facing the same problem. When this screen starts coming all application opened at that point of time lost the connection and asks to go to the hub and when I click go the hub button this error screen comes. At the last I have to restart Qlik Sense.
I've got the same problem, but it happened when I tried to create an ODBC connection with Mysql. As soon as I created the connection it crashed, and now it crashes every time I try to open the concerned app. Of course it only tells me : ErrorCode.12004