Visual Studio crashes when opening Mission Planner design

I have downloaded the source code from Mission Planner.
I managed to succesfully open it and build it with Visual Studio 2015. But, whenever I try to open FlightPlanner.cs or FlightData.cs in design mode, it crashes.
Does someone know how to fix this?

switch to vs 2017, and make sure you are using current master code

Well, the problem also ocurred in Visual Studio 2017 (that was the reason why I changed to VS15). Already using the current master code also.

Updating: FlightPlanner.cs appears to be loading okay, but FlightData still does not load in Design Mode.