Polylines are not updated because the new added hasChanged() method in _PolylineUpdates.from(), always found the previous and current polyline being the same.
As a test, returnig true from hasChanged() restore the correct behavior.

The polyline was used to track the user route on the map, the only thing changing being the number of points.
Now, to restore the behavior, the PolylineId() must be unique, causing the old one to be removed.