Fran, actually the "leap second" they had to insert into the GPS constellation recently actually screwed up several GPS manufacturers whose algorithms could not account for the event. Those receivers corrected after the month the leap second was inserted, but it did make a mess with some GPS receivers.
Again, and I know I've said this over and over again, the GPS constellation of satellites is under the control of the USAF. They have the ability to selectively "turn off" portions, or all, of the GPS transmissions and be usable only to the US and it allies via the use of crypto keys. I've had to load these keys into radio and navigation equipment. The USAF is always sending up replacement GPS satellites each with new technology included. The cost of maintaining the current GPS system is something only a government could afford.