Have you created a Widget and type to view the position on the SmartDashboard? Without one, nothing should happen when you call "SmartDashboard.putData()", so I'm not sure why the SmartDashboard freezes.
We wrote a few Sendables for our robot, if you want to see examples:
WheelController
Robot Code (Sendable)
SmartDashboard Widget
SmartDashboard Type
ParameterCommand
Robot Code (Sendable)
SmartDashboard Widget
SmartDashboard Type
Let me know if you want explanations of how the code works.