Perhaps the times when there is no XYZ output are times when there is no solution status? No solution = no output.
see the comments here:
If this indeed is what is happening, then you may need to create some code to repeat the last known coordinate, or maybe predict and project your traveled path.
It would not be good for Reach to blindly output a coordinate when there is no current coordinate solution, but you can do that if it fits your use case.