Steps to reproduce:

• Connect device, e.g. RasberryPi with wireless connection (Edit -> Preferences -> Devices -> Add -> Start wizard to add device ...)
• Create some project
• Select Kit Boot2Qt device
• Click Run
• Wait untill deployed and running on device
• Do something that causes the connection to device break: turn off the raspberry, disconnect you computer from internet
• Click Stop button in Application Output (View -> Output -> Application output)
• -> Design Studio goes into not responding state

Another way to reproduce it:
Steps to repro

1. Open QDS in network A and configure a B2Qt device in that network
2. Close apps and move setup to network B
3. Open QDS
4. Open a project for editing

Expected result: Project opens OK

Actual result: QDS is stuck on the busy indicator

PS: Qt Creator 17.0 still has the same problem