lldb debugger stops working

Steps to reproduce:

• create a Qt Widget Application from template
• add a QPushButton and connect the clicked() signal with a slot
• set breakpoint into the slot for the QPushButton-click
• start debugging
• click onto the button to trigger the breakpoint
• inside the Locals unfold: this -> Ui_MainWindow -> pushButton -> properties

Current result:

• Application output prints out 'libc++abi.dylib: pure virtual method called' several times
• Locals view is shortly displaying some stuff of the QAbstractButton, within a split of a second the view is completely purged
• hitting 'Stop Debugger' does now no more work (Interrupt/Stop buttons are greyed out, but debugging is still in progress)
• you have to invoke 'Debug' -> 'Abort Debugging' or click the 'Stop' button on the Application Output widget