Hi Guys,
I originally thought this was a problem with grasshopper but after repeating the grasshopper process in plain Rhino the same thing happens there:
I have a curve, positioned about 3600 mm from the origin which seems normal: When I run the SelBadObjects command it doesn’t get selected.
Also whenever you move an object via the gumball rhino deletes it and then adds it back to the document with the transform value from the gumball, so it seems your polycurve does not satisfy rhinos inner validity checks there.
Here is a naive ghpython component which checks arc segments inside polycurves if they are over a specified maximum radius and replace them with straight lines from the arc start to arc end points.
Also in my opinion is it good that rhino marks such polycurves is bad objects (although not consistently) since no CNC or LaserCutter will process arcs of such radii and angles.