I was thinking on reading the topic title that a couple of the existing satellites in a different orbit over the polar areas might have become degraded ... however it reads more like that the degree of inaccuracy has been quantified by Canada's military and the poor accuracy is being blamed on low angles from the existing satellite orbits. Low angles would assume near equatorial orbits and not multi-planar as they are [1] As such, it causes me to wonder if the issue isn't more widespread.

[1] https://www.gps.gov/space-segment